Remove unused method update_fixed_ip_lease_expiration

This should have been log removed here:
	Ifcb4f093c92904ceb896438987d53e692eb7fb26

Change-Id: I9395fea531365b82a0cd16f29d6392199e2d9c22
Closes-bug: #1287407
Merge "Remove unused method update_fixed_ip_lease_expiration"