Do not create a bridge device for nova_fixed anymore

nova-network support got removed and the nova_fixed network is now only used by
quantum. In ovs mode the ovs bridges will be created by the quantum cookbook.
In linuxbridge mode the linuxbridge agent will manage it. If crowbar already
created the bridge this would not work.
Use bonding mode 5 (balance-tlb) by default

The old default (mode 6, balance-alb) does not work reliably when the
bond device is attached to a bridge. See e.g.:
https://bugzilla.redhat.com/show_bug.cgi?id=560588#c14

Some of those issue have been fixed in very recent kernels (3.8 and later), but
we should not rely on that. (SLES 11 is that 3.0.x, Ubuntu 12.04 is 3.2.x or
3.5.x)

This patch also removes the redundant "team_mode" settings from the
conduit_list for the team mode. The network barclamp will default to what's
configured in the global "mode" setting in that case.
Merge pull request #183 from rhafer/release/pebbles/master

Do not create a bridge device for nova_fixed anymore
Merge pull request #185 from rhafer/fix/default-bonding-mode

Use bonding mode 5 (balance-tlb) by default