Make restart count test serial

This test asserts that there are no failing datavolumes in the cluster,
so it can't run in parallel to negative tests, and thus has to remain
serial.

Signed-off-by: Alex Kalenyuk <akalenyu@redhat.com>

tests/import_test.go

@@ -955,7 +955,7 @@ var _ = Describe("[rfe_id:1115][crit:high][vendor:cnv-qe@redhat.com][level:compo
 		Expect(dv.Status.RestartCount).To(BeNumerically("==", 0))
 	})
 
-	It("[test_id:3996] Import datavolume with bad url will increase dv retry count", func() {
+	It("[test_id:3996] Import datavolume with bad url will increase dv retry count", Serial, func() {
 		if f.IsPrometheusAvailable() {
 			dataVolumeNoUnusualRestartTest(f)
 		}