Clean up adb_trace_init.

Old code was a mess for splitting a string and then searching a list
when they really wanted a map.

To more closely match ANDROID_LOG_TAG, only use a space separated list
rather than space/colon/semi-colon/comma.

Change-Id: I915ff4968e42d5f8dec1b43b6eacc0c8d7b44d7b