This permits us to move shared code for looking up system
folder names to emailcommon, which is also in this change.
Also renames emailcommon2 to emailcommon.
This is part of a multi-project submit with
I4a071a07c3e33aaa4ea404eb66a8db1eabc9ef0e and
I5746c0353783f9b29d52d6540472588c6542a6a2.
Bug: 8383232
Change-Id: I6c6eec4f1bcf2abd54c1ed05da1add8d894ee403