Add method that checks the Binder status of ImsConfig

Adds a method to check whether or not the ImsConfig
binder has died.

Bug: 62723694
Test: maual, follow bug procedure
Merged-In: I0ecd6a43d4375d3ac4d7d54b3d437832c0221f05
Change-Id: I9df6533e7e7dc69487cea50fada6c89599b031a3