BTM_SEC: Change pairing state when ACL is already connected

Returning early from btm_sec_dd_create_conn skipped the state
update, which results in failed pairing in some cases.

Bug: 345552848
Test: atest RfcommTest
Flag: EXEMPT, simple bug fix with a test
Change-Id: I00828ed796411055eef042f7d68c751450e7c38a