use message in android.AssertStringMatches()

function does not currently use the message argument  passed to it.
outputting this as part of the error message would be helpful for any
failures.

Change-Id: I5307df1567e79d85f81edd5a9eb3d4a093041535

android/test_asserts.go

@@ -148,7 +148,7 @@ func AssertStringMatches(t *testing.T, message, s, expectedRex string) {
 		return
 	}
 	if !ok {
-		t.Errorf("%s does not match regular expression %s", s, expectedRex)
+		t.Errorf("%s: %s does not match regular expression %s", message, s, expectedRex)
 	}
 }