tests: do not include skipped tests in failedTests

We recognize three return values from tests:
* OK    -> 0
* SKIP  -> EXIT_AM_SKIP
* ERROR -> anything else

Also check for EXIT_AM_SKIP when building a bitmap of failed tests,
otherwise the skipped tests would be printed in the suggested range
of tests that shoud be re-run.
Reported-by: NPeter Krempa <pkrempa@redhat.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Fixes: cebb468eReviewed-by: NPeter Krempa <pkrempa@redhat.com>

tests/testutils.c

@@ -172,7 +172,7 @@ virTestRun(const char *title,
             fprintf(stderr, "!");
     }
 
-    if (ret != 0)
+    if (ret != 0 && ret != EXIT_AM_SKIP)
         ignore_value(virBitmapSetBitExpand(failedTests, testCounter));
 
     g_unsetenv("VIR_TEST_MOCK_TESTNAME");