Fix to add existing connection for emergency only account.

If Telephony registers emergency account with emergency
calls only, this account will be excluded from the call
capable accounts.

To fix it, include 'CAPABILITY_EMERGENCY_CALLS_ONLY'
emergency account in the call capable phone accounts.

Bug: 122491374
Test:Manual
Change-Id: Iff630e5ba1faa51c1a13c601752dc6ec71806c5c