It's said a wicketkeeper does not stand against opposition batsmen, he stands against bowlers of his own team. It takes lots of time and practice to get used to a particular set of bowlers. I think it won't be fair or wise to drop Mushfiq now and bring Mashud or Dhiman out of wilderness to stand in the next match.
Mushfiq developed his keeping skills enough to retain his place for next test. However, we surely need a keeper for ODIs who can also contribute with bat. As I said in another thread, it's time the selectors bring Dhiman in the national team camp and have him train with the team for next couple of weeks. If Mushfiq doesn't show improvement in his batting in next test, bring Dhiman in for the ODI series.