change command to --restore and perform backup in zenpack install

```
[zenoss@f5b8247ed50d ~]$ zenpack --list
ZenPacks.zenoss.ApacheMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.ApacheMonitor-2.1.4-py2.7.egg)
ZenPacks.zenoss.DellMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DellMonitor-2.2.0-py2.7.egg)
ZenPacks.zenoss.DeviceSearch (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DeviceSearch-1.2.0-py2.7.egg)
ZenPacks.zenoss.DigMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DigMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.DnsMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DnsMonitor-2.1.0-py2.7.egg)
ZenPacks.zenoss.FtpMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.FtpMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.HPMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.HPMonitor-2.1.0-py2.7.egg)
ZenPacks.zenoss.HttpMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.HttpMonitor-2.1.0-py2.7.egg)
ZenPacks.zenoss.IRCDMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.IRCDMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.JabberMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.JabberMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.LDAPMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.LDAPMonitor-1.4.1-py2.7.egg)
ZenPacks.zenoss.LinuxMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.LinuxMonitor-1.3.0-py2.7.egg)
ZenPacks.zenoss.Memcached (broken)
ZenPacks.zenoss.Microsoft.Windows (/opt/zenoss/ZenPacks/ZenPacks.zenoss.Microsoft.Windows-2.1.3-py2.7.egg)
ZenPacks.zenoss.MySqlMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.MySqlMonitor-3.0.2-py2.7.egg)
ZenPacks.zenoss.NNTPMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.NNTPMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.NtpMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.NtpMonitor-2.2.1-py2.7.egg)
ZenPacks.zenoss.PythonCollector (/opt/zenoss/ZenPacks/ZenPacks.zenoss.PythonCollector-1.6.0-py2.7.egg)
ZenPacks.zenoss.XenMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.XenMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.ZenJMX (/opt/zenoss/ZenPacks/ZenPacks.zenoss.ZenJMX-3.11.0-py2.7.egg)
ZenPacks.zenoss.ZenossVirtualHostMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.ZenossVirtualHostMonitor-2.4.0-py2.7.egg)
[zenoss@f5b8247ed50d ~]$ zenpack --restore                                                                      
INFO:zen.ZenPackCmd:restoring zenpacks
INFO:zen.ZenPackCmd:looking for /opt/zenoss/.ZenPacks/ZenPacks.zenoss.Memcached-1.3.0*
INFO:zen.ZenPackCMD:Previous ZenPack exists with same name ZenPacks.zenoss.Memcached
[zenoss@f5b8247ed50d ~]$ zenpack --list                                                                         
ZenPacks.zenoss.ApacheMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.ApacheMonitor-2.1.4-py2.7.egg)
ZenPacks.zenoss.DellMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DellMonitor-2.2.0-py2.7.egg)
ZenPacks.zenoss.DeviceSearch (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DeviceSearch-1.2.0-py2.7.egg)
ZenPacks.zenoss.DigMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DigMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.DnsMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.DnsMonitor-2.1.0-py2.7.egg)
ZenPacks.zenoss.FtpMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.FtpMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.HPMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.HPMonitor-2.1.0-py2.7.egg)
ZenPacks.zenoss.HttpMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.HttpMonitor-2.1.0-py2.7.egg)
ZenPacks.zenoss.IRCDMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.IRCDMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.JabberMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.JabberMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.LDAPMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.LDAPMonitor-1.4.1-py2.7.egg)
ZenPacks.zenoss.LinuxMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.LinuxMonitor-1.3.0-py2.7.egg)
ZenPacks.zenoss.Memcached (/opt/zenoss/ZenPacks/ZenPacks.zenoss.Memcached-1.3.0-py2.7.egg)
ZenPacks.zenoss.Microsoft.Windows (/opt/zenoss/ZenPacks/ZenPacks.zenoss.Microsoft.Windows-2.1.3-py2.7.egg)
ZenPacks.zenoss.MySqlMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.MySqlMonitor-3.0.2-py2.7.egg)
ZenPacks.zenoss.NNTPMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.NNTPMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.NtpMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.NtpMonitor-2.2.1-py2.7.egg)
ZenPacks.zenoss.PythonCollector (/opt/zenoss/ZenPacks/ZenPacks.zenoss.PythonCollector-1.6.0-py2.7.egg)
ZenPacks.zenoss.XenMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.XenMonitor-1.1.0-py2.7.egg)
ZenPacks.zenoss.ZenJMX (/opt/zenoss/ZenPacks/ZenPacks.zenoss.ZenJMX-3.11.0-py2.7.egg)
ZenPacks.zenoss.ZenossVirtualHostMonitor (/opt/zenoss/ZenPacks/ZenPacks.zenoss.ZenossVirtualHostMonitor-2.4.0-py2.7.egg)
```
Should this be in a finally block instead?