AVDTP: Make sure the UUID of the SCB is initialized before discovering

When parsing remote SEP capabilities, we check the UUID value in the AV
SCB to choose the SEP, and this parameter was assigned when AVDTP was
reconnecting from the phone side. This change also assigns the UUID to
make sure the stack can find remote's SEPs correctly when reconnected
by the remote.

Bug: 137631786
Test: make AVDTP reconnection from the peer side
Change-Id: Ib2fa6e76de31bab1131c024e9f76433f3fd8b60a