BUG: GH12050 Setting values on Series using .loc with a TZ-aware DatetimeIndex fails
Fixes https://github.com/pydata/pandas/issues/12050 .

Taking just the values of an index object looses the timezone information.

Fix has been derived from similar code in the method _getitem_iterable around line 980 of indexing.py .

Somebody with a better knowledge about the interplay of all the functions should comment before merging.
 tests!
 Is this one good enough? Or should I also test for variations?
 pls also add a release note (bug fixes)
 - Fixed the tests.
- Added release notes.
- Rebased onto current master.
- Squashed

Ready for merging from where i sit.
 merged via https://github.com/pydata/pandas/commit/41821050049de766b07ed068b32839718544e39e

thanks!
