fix for controls that hide if keyboard scrubbing

In version 2.9, I reported issue mediaelement#548, that controls hide when using
keyboard to scrub even if the alwaysShowControls option is set to
"true." Pull request mediaelement#569 merged this fix, but did so in the /build
directory. It appears that fix did not move forward with versions and
the issue is occurring in the latest version. Adding fix in the /src
directory so that future builds get the fix.

src/js/mep-player.js

@@ -391,7 +391,7 @@
 
 			doAnimation = typeof doAnimation == 'undefined' || doAnimation;
 
-			if (!t.controlsAreVisible)
+			if (!t.controlsAreVisible || t.options.alwaysShowControls)
 				return;
 
 			if (doAnimation) {