Fix bta_dm_disc stuck in cancelling state

When service discovery is cancelled, we still expect to receive some sort of
result either from SDP or GATT, and won't move to any different state
until we do. We are stuck in BTA_DM_SEARCH_CANCELLING state.
If service discovery fails to establish GATT connection, or if it was to
fail i.e. due to peer disconnection, we should move on to next device
trying to discover services. Without this patch, we stay stuck until
Bluetooth restart.

Bug: 318580354
Bug: 319890673
Test: Try bonding, disconnect device while GATT service discovery is
scheduled but not yet done
Change-Id: I7c59701831d0b9288dea9eea375769db357fb7bc

Change-Id: I5a57789639b8fb6a55539e1e5c63c7530292336e