AlarmManager: Reject non-olson timezones for targetSdk >= M

This has caused a lot of grief, confusion and outright broken
behaviour due to the fact that the Posix spec and the Java spec
define conflicting interpretations of "custom" timezones like
GMT+5:30 (eastern hemisphere for java, western for posix).

bug: 19987403
bug: 19106773
Change-Id: Ia9b007067bb175b0805d4262f17390a0bd98d927