Fix leak of remote driver if final 'CLOSE' RPC call fails

Fix leak of remote driver if final 'CLOSE' RPC call fails

When closing a remote connection we issue a (fairly pointless)
'CLOSE' RPC call to the daemon. If this fails we skip all the
cleanup of private data, but the virConnectPtr object still
gets released as normal. This causes a memory leak. Since the
CLOSE RPC call is pretty pointless, just carry on freeing the
remote driver if it fails.

* src/remote/remote_driver.c: Ignore failure to issue CLOSE
  RPC call