Corrected formatting for 2445 if timezone is UTC

According to RFC 2445 if time is in UTC timezone it should be ended with Z character. See https://github.com/android/platform_frameworks_base/blob/master/core/jni/Time.cpp#L148
Added test for 2445 formating with UTC Timezone
Merge pull request #466 from ymkawb/patch-1

Corrected formatting for 2445 if timezone is UTC