Only try to unassign an IP address if it could succeed
Only try to unassign an IP address if it could succeed


Former-commit-id: 06f5db42278b264d6dde96145e5bbc3da345be46
tomdee/libcalico,insequent/libcalico,TrimBiggs/libcalico,alexhersh/libcalico,projectcalico/libcalico,projectcalico/libnetwork-plugin,djosborne/libcalico,caseydavenport/libcalico,Symmetric/libcalico,tomdee/libnetwork-plugin,robbrockbank/libcalico,L-MA/libcalico,plwhite/libcalico,TrimBiggs/libnetwork-plugin,TrimBiggs/libnetwork-plugin