Catch BadTokenException and continue in clearInsetofPreviousIme.

This is a follow up CL for Ib04967f39b2529251e4835c42e9f99dba2cf43f2.
As well explained in the I2c21573cf972145ab08e66604cdb9344139a3f31,
the race condition here cannot be avoided without an unacceptable
performance penalty.  For now, we follow the same way.

Bug: 21600287
Change-Id: I0ffdf8bf7e8a53cf8aba1339024b32da65d4f32d