Cannot swap active and background calls after failing to merge.

When a conference call merge fails, an attempt to swap between the active
and held calls will fail; resuming the bg call fails.  The problem is
switchWaitingOrHoldingAndActive swaps the FG/BG ImsCall references before
getting positive confirmation that they suceeded.

1. When initiating a call swap, keep track of the call we expect to
resume.  In the resume success method, check if we resume a call other than
the one we expect to.  In the resume fail method, check if we failed to
resume the call we expected to.  In both cases, switch the FG/BG call
references back to ensure that state signaling is handled properly.
2. Trigger a notifySuppServiceFailed on the phone to report that the
resume failed; this is used by Telephony to display a failure message.

Bug: 18656014
Change-Id: I8e67389601861a933c648ca876d4e8a12ef54fee