Stop checking for resources.arsc in shouldCreateIdmap

The check for resources.arsc in the target apk was a fix for when
we supported legacy themes (t-mobile engine).  Since support for
legacy themes was dropped in cm-12.0, this patch just adds extra
overhead and results in ANRs in some cases.

Change-Id: I275d9ccd3e67eead91f3e8c39a2b64f31f473ed3
(cherry picked from commit 28258a1f)