Bonded bridge slave support

Tested with the following config:
<pre>
# cobbler system report --name=bbstest
Name                           : bbstest
TFTP Boot Files                : {}
Comment                        : 
Enable gPXE?                   : False
Fetchable Files                : {}
Gateway                        : 192.168.1.1
Hostname                       : bbstest
Image                          : 
IPv6 Autoconfiguration         : False
IPv6 Default Device            : 
Kernel Options                 : {}
Kernel Options (Post Install)  : {}
Kickstart                      : <<inherit>>
Kickstart Metadata             : {}
LDAP Enabled                   : False
LDAP Management Type           : authconfig
Management Classes             : []
Management Parameters          : <<inherit>>
Monit Enabled                  : False
Name Servers                   : []
Name Servers Search Path       : []
Netboot Enabled                : True
Owners                         : ['admin']
Power Management Address       : 
Power Management ID            : 
Power Management Password      : 
Power Management Type          : ack_manual
Power Management Username      : 
Profile                        : f16-x86_64
Proxy                          : <<inherit>>
Red Hat Management Key         : <<inherit>>
Red Hat Management Server      : <<inherit>>
Repos Enabled                  : False
Server Override                : <<inherit>>
Status                         : production
Template Files                 : {}
Virt Auto Boot                 : 0
Virt CPUs                      : 1
Virt Disk Driver Type          : <<inherit>>
Virt File Size(GB)             : 5
Virt Path                      : <<inherit>>
Virt RAM (MB)                  : 768
Virt Type                      : kvm
Interface =====                : br0
Bonding Opts                   : 
Bridge Opts                    : 
DHCP Tag                       : 
DNS Name                       : 
Master Interface               : 
Interface Type                 : bridge
IP Address                     : 192.168.1.224
IPv6 Address                   : 
IPv6 Default Gateway           : 
IPv6 MTU                       : 
IPv6 Secondaries               : []
IPv6 Static Routes             : []
MAC Address                    : 
Management Interface           : True
MTU                            : 
Subnet Mask                    : 255.255.255.0
Static                         : True
Static Routes                  : []
Virt Bridge                    : br0
Interface =====                : bond0
Bonding Opts                   : mode=1
Bridge Opts                    : 
DHCP Tag                       : 
DNS Name                       : 
Master Interface               : br0
Interface Type                 : bonded_bridge_slave
IP Address                     : 
IPv6 Address                   : 
IPv6 Default Gateway           : 
IPv6 MTU                       : 
IPv6 Secondaries               : []
IPv6 Static Routes             : []
MAC Address                    : 
Management Interface           : False
MTU                            : 
Subnet Mask                    : 
Static                         : False
Static Routes                  : []
Virt Bridge                    : br0
Interface =====                : eth1
Bonding Opts                   : 
Bridge Opts                    : 
DHCP Tag                       : 
DNS Name                       : 
Master Interface               : bond0
Interface Type                 : bond_slave
IP Address                     : 
IPv6 Address                   : 
IPv6 Default Gateway           : 
IPv6 MTU                       : 
IPv6 Secondaries               : []
IPv6 Static Routes             : []
MAC Address                    : 00:16:3e:72:78:da
Management Interface           : False
MTU                            : 
Subnet Mask                    : 
Static                         : False
Static Routes                  : []
Virt Bridge                    : br0
Interface =====                : eth0
Bonding Opts                   : 
Bridge Opts                    : 
DHCP Tag                       : 
DNS Name                       : 
Master Interface               : bond0
Interface Type                 : bond_slave
IP Address                     : 
IPv6 Address                   : 
IPv6 Default Gateway           : 
IPv6 MTU                       : 
IPv6 Secondaries               : []
IPv6 Static Routes             : []
MAC Address                    : 00:16:3e:67:d8:29
Management Interface           : False
MTU                            : 
Subnet Mask                    : 
Static                         : False
Static Routes                  : []
Virt Bridge                    : br0
</pre>

Tested VM has the following config:

<pre>
bond0     Link encap:Ethernet  HWaddr 00:16:3E:67:D8:29  
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:502 errors:0 dropped:48 overruns:0 frame:0
          TX packets:87 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:71088 (69.4 KiB)  TX bytes:9014 (8.8 KiB)

br0       Link encap:Ethernet  HWaddr 00:16:3E:67:D8:29  
          inet addr:192.168.1.224  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::216:3eff:fe67:d829/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:329 errors:0 dropped:0 overruns:0 frame:0
          TX packets:98 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:24258 (23.6 KiB)  TX bytes:10868 (10.6 KiB)

eth0      Link encap:Ethernet  HWaddr 00:16:3E:67:D8:29  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:525 errors:0 dropped:48 overruns:0 frame:0
          TX packets:117 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:72606 (70.9 KiB)  TX bytes:13154 (12.8 KiB)

# ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_req=1 ttl=255 time=0.352 ms
64 bytes from 192.168.1.1: icmp_req=2 ttl=255 time=0.486 ms
64 bytes from 192.168.1.1: icmp_req=3 ttl=255 time=0.441 ms
^C
--- 192.168.1.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 0.352/0.426/0.486/0.058 ms
</pre>

The eth1 interface doesn't seem to be showing up, most likely due to the fact that I have two interfaces attached to the same virtual bridge. This doesn't have anything to do with cobbler, as I have verified the sysconfig files are generated correctly for each physical interface.

More review on this would be appreciated, though I believe it is safe to merge into master.