Don't deallocate network if destroy time out

Fixes bug #1169057
Sames as bug 1180178, if libvirt returns time out error during destroy
an instance, we also can't deallocate the network of the instance,
otherwise the fixed ip of it may be re-used by another new instance,
and resulted in the new instance can't be accessed by the fixed ip.

Change-Id: I04dfd21bb1b7168abc71f39e836126a11dad6d8d
Merge "Don't deallocate network if destroy time out"