rpc: virNetClientNew: fix socket leak on error path

rpc: virNetClientNew: fix socket leak on error path

if virNetClientNew finishes with error before sock is set
to client object then sock does not get unrefed. This is
unexpected by function clients like virNetClientNewUNIX.
Let's make sure sock gets unrefed on any error path.

Next some clients like virNetClientNewLibSSH2 try to unref
sock on virNetClientNew errors. This is not correct even
before this patch because in some cases virNetClientNew
unrefed sock on error path by itself. Let's give up
sock managment to virNetClientNew entirely.

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>