RFCOMM: Always be the DISC initiator in the DISC_WAIT_UA state

Aggressively proceed DISC if we've already in the DISC_WAIT_UA state.
This avoids a meaningless timeout which all services based on RFCOMM
would be blocked during.

Bug: 343640447
Bug: 350839022
Test: mmm packages/modules/Bluetooth
Test: manual verify no timeout on RFCOMM disconnection,
      see b/343640447#comment7
Flag: com.android.bluetooth.flags.rfcomm_always_disc_initiator_in_disc_wait_ua
Change-Id: I52b46b758cbd588dd5731c81d6620d29a0095719