Fix shouldProcessCall in ImsManager

There can be call attempts made before the ims service
is  initialized. In this case, shouldProcessCall should
throw an exception, else it might result in subsequent call
failure in IMS.

Bug: 232514463
Test: atest ImsManagerTest
Change-Id: I81a25250a65bf6af0910c57f093ebbc71bad1dba
(cherry picked from commit 7b6fb80d5ec80d4ef996453f16403727d17ff279)
2 files changed