transport: handle BAP Enabling state correctly when resuming

transport: handle BAP Enabling state correctly when resuming

If BAP stream is in Enabling state when transport acquire is attempted,
we should wait for bap_state_changed to emit the completion event.

transport->resume() is only called with new owner with no
owner->pending, and shall return nonzero completion id on success.
Currently if BAP stream is Enabling, it returns zero which fails the
acquire operation.

To fix this, return valid completion id in this case instead.  Also keep
track of the g_idle_add resume id, so that we don't try to give it to
bt_bap_stream_cancel.

Fixes sound server getting spurious Not Authorized errors when trying to
acquire a pending transport.  This can happen on BAP server: linked
transports become pending when the first of the two enters Streaming. If
sound server tries to acquire the other linked transport whose stream is
still Enabling, the acquire fails (media_owner_free +
btd_error_not_authorized).

Log:
===============================================================
profiles/audio/transport.c:bap_state_changed() stream 0x25c2880: qos(2) -> enabling(3)
...
profiles/audio/transport.c:bap_state_changed() stream 0x25cc590: qos(2) -> enabling(3)
...
src/shared/bap.c:bap_stream_state_changed() stream 0x25cc590 dir 0x01: enabling -> streaming
profiles/audio/bap.c:bap_state() stream 0x25cc590: enabling(3) -> streaming(4)
profiles/audio/transport.c:bap_state_changed() stream 0x25cc590: enabling(3) -> streaming(4)
/org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/fd1: fd(36) ready
profiles/audio/transport.c:transport_update_playing() /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/fd1 State=TRANSPORT_STATE_IDLE Playing=1
profiles/audio/transport.c:transport_set_state() State changed /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/fd1: TRANSPORT_STATE_IDLE -> TRANSPORT_STATE_PENDING
profiles/audio/transport.c:transport_set_state() State changed /org/bluez/hci0/dev_XX_XX_XX_XX_XX_XX/fd0: TRANSPORT_STATE_IDLE -> TRANSPORT_STATE_PENDING
profiles/audio/transport.c:media_owner_create() Owner created: sender=:1.1242
profiles/audio/transport.c:media_owner_free() Owner :1.1242
===============================================================