tests: fix incorrect status handling by virsh-self-test

tests: fix incorrect status handling by virsh-self-test

The virsh-self-test script compared the test's return code with 1 and only if
the return code matched this value then the test was marked as failed. Problem
is that SIGSEGV returns 139 (or 11 to be precise, since shell reserves the MSB
for abnormal exit signaling) which passes the check just fine and test then
appears as successful which it most certainly wasn't.
Therefore, flip the logic to compare against 0 instead and every other result
will be treated as a failed test case.

Signed-off-by: Erik Skultety <eskultet@redhat.com>