Fix for Settings timezone names when boot time is wrong

Avoid the libcore.icu.TimeZoneNames cache for time zone
settings by using ICU4J: it will not use timezone names
that were cached and can be missing / incorrect if the
clock was incorrect at zygote start. Instead, the devices
current time will be used when generating the names.

This change values correctness over performance. ICU does
perform its caching of names so I don't expect any
degredation to be noticeable.

Bug: 20879084
Bug: 26158280
Bug: 21015187
Bug: 26182881
Change-Id: I9f68e3e5232434949468305bbdaf7e697e58da1e