URIUtils loads error messages unnecessarily

[Capstan]

URIUtils.SCHEME_CHECKER.check() loads the error message bundle (which spawns a Thread to get the message source for the locale) even if the check would succeed. If this was a Future then it could be lazily loaded only if one of the checks failed.

This was discovered when upgrading json-schema-validator from v1.6.2 to v2.2.10, since the test harness we used for "small" tests inhibits thread creation, and meant that validator tests now must be promoted to "medium".