Bluetooth: Fix LE Connection refcnts

Some rebalancing of refcnts due to issues found during testing:

Refcnt was not being released on security completion, if local side
was paired but the remote side had deleted the pairing info, and then
the re-pair failed to complete successfully.

Additionally, the refcnt was not held-released properly if pairing
was initiated due to the client socket being opened with security
level elevated from the start.

Change-Id: I120fed4dc74035d280781ca949a23d4cbcfa3f3e
CRs-fixed: 335993
Signed-off-by: Brian Gix <bgix@codeaurora.org>