KNOX-466: Log exception stack traces at INFO level when they reach gateway servlet

(cherry picked from commit 0edaec6e33f68f6fe68b2e63e6f867401f194c2d)
KNOX-467: Unit tests failing on windows

(cherry picked from commit 4c7ddb58ff4d9f655e3e7f919a6ac8d91bdcbb06)