CLOUDSTACK-4575: Portable IP: disassociating a transferred public IP  fails
The code is excessively complicated and convoluted.
 DisassociateIP ->
     Revoke Rule -> {FW, PF{incl SNAT}, LB, RA VPN} ->
        -> Send IpAssoc (false) to VR
     Send all config to VR again
        -> Send IpAssoc(false) to VR again  <---- fails here since it cannot find the VLAN for the IP since it is already gone
        -> Mark Ip as released

The workaround fix would be to not throw an exception in CitrixResourceBase if it is disassociate and the VLAN does not exist on the XS host.

Signed-off-by: Chiradeep Vittal <chiradeep@apache.org>