liblog: free event tag map in __android_log_close()

There is no leak since a reference always remained and could get
reused.  It just makes sense to also close the event tag map as well
if logging is closed.  If we close we also have to fix a tagArray
leak in android_closeEventTagMap().

NB: __android_log_close() already makes an assumption that another
thread is not logging at the same time, which is true in all callers
at this time.  There are some partial mitigation strategies if
__android_log_close() is called asynchronously, but not completely
solved at the cost of a lock for every logging call.

Test: gTest liblog-unit-tests
Bug: 30963384
Bug: 31456426
Change-Id: Ib76ad9302dba4d3f35250213f4dfef22498af238