Delete duplicate internal devices in router namespace

When neutron router-interface-delete <router> <subnet> is ran
during L3-agent restart, the agent may fail to delete the old
internal device. After the restart, when the command "neutron
router-interface-add <router> <subnet>" is ran again, the
router ends up having two internal devices configured with the
same IP address.

Closes-Bug: #1244853
Change-Id: I0d7e2db6aa7dae26d0fc3fe1b1527762cb1e3b23
Fix usage of save_and_reraise_exception

Set reraise=False for the cases where the purpose of exception
handler is to reraise proper type of exception

Change-Id: Id6595ba1e160b9033d519ded16e0fbd2f91ccb5d
Closes-Bug: #1288188
Merge "Fix usage of save_and_reraise_exception"
Merge "Delete duplicate internal devices in router namespace"