Ensure CallId is not null when connection creation is complete.

When calling "get" on the mConnectoinById map, a null callId will result
in an NPE.

In findConnectionForAction, defaulting to returning the "null" connection
which is the same behavior as if it isn't found.
In notifyCreateConnectionComplete, specifically checking if the callId
is null and skipping the onCreateConnectionComplete callback.
This scenario is possible if the connection is remove from the
ConnectionService before the connection complete callback comes back from
Telecom.

Test: Manual
Fixes: 62588734
Merged-In: I1de7a0a4cc9c630019e38b8154bfc1d470f56ae3
Change-Id: Ie610c51155ed417e0f916000fe20e4484bdb6603