e2e: yet more cleanup of BeTrue/BeFalse

Thanks to Paul for teaching me about HaveKey()

Signed-off-by: Ed Santiago <santiago@redhat.com>

test/e2e/containers_conf_test.go

@@ -245,7 +245,7 @@ var _ = Describe("Podman run", func() {
 		session := podmanTest.Podman([]string{"run", "--dns-search=.", ALPINE, "cat", "/etc/resolv.conf"})
 		session.WaitWithDefaultTimeout()
 		Expect(session).Should(Exit(0))
-		Expect(session.LineInOutputStartsWith("search")).To(BeFalse())
+		Expect(session.OutputToStringArray()).To(Not(ContainElement(HavePrefix("search"))))
 	})
 
 	It("podman run use containers.conf search domain", func() {