Catch all exceptions when calling startCheckpoint().

The existing code in vold throws exceptions based on errno,
which can't be mapped to binder exceptions, and hence throw a
RuntimeException instead. To prevent bringing system_server down with
these, catch all exceptions for now.

Bug: 130190815
Test: builds
Change-Id: I3f5aaa12a01e4748ccb2b2467416c49645315cfb