Indicate RFCOMM connection complete when modem signal is confirmed

This change is applied only for offloaded socket

Bug: 342012881
Bug: 393594567
Test: m com.android.bt
Flag: com.android.bluetooth.flags.indicate_rfcomm_connection_complete_after_msc
Change-Id: I3ec8652cb19a7e4dc1bd1f6e63d807374d68e503