Combine LockTask transition with previous

Combine the transition that exists with a new transition that start
LockTask, to make sure that any issue from starting it is caught as part
of the previous transition.

Bug: 442319823
Test: m
Flag: EXEMPT BUGFIX
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:a1af0fb80811df3c334cd11f94224a799fb6e97d
Merged-In: I4c27eadb55b466244fb992792cad98f6ca62bdb4
Change-Id: I4c27eadb55b466244fb992792cad98f6ca62bdb4