HFP: fix collision for the outgoing and incoming connection

Since the HF incoming connection and the HF outgoing connection use the
same HF control block (p_scb) at the same time, the case will cause the
btif_hf_cb flag going wrong due to collision. Then it will trigger a
crash due to a check failure when executing BTA_AG_OPEN_EVT. The patch
will ignore the outgoing connection when the connection
collision is happening.

Bug: 143128949
Test: manual

Change-Id: Id5495bd3ecb1ed9e03de5bd74a61ab102604eaae
Merged-In: Id5495bd3ecb1ed9e03de5bd74a61ab102604eaae