b78c9c8 tests: Fix incorrect check for virNetServerClientClose call

Authored and Committed by John Ferlan 6 years ago
    tests: Fix incorrect check for virNetServerClientClose call
    
    Commit id '6df5d777' somehow during the move from one branch to
    another added an erroneous '!'...
    
    Signed-off-by: John Ferlan <jferlan@redhat.com>