Add plumbing for the 911 redial

Provide a mechanism to swap out the original connection when the lower
layers trigger a redial.

Bug: 111235453
Test: manual (modify IMS stack locally to always return the 380 error
when dialing in airplane mode)

Change-Id: Ie1cab49f040dd2b34b775bd9e5d7f97fbf7aafa9
1 file changed