Avoid skipping SDP after link key derivation

Use Case:
In case of cross key derivation of BR link key from a secure LTK,
the corresponding BR transport needs to go through the SDP routine
and alert the upper layers regarding the bond completion of the
BR transport. This specific procedure is currently getting skipped
in an attempt to prevent spurious link key notifications from causing
bond state changes

Fix:
Added an additional check to make sure that the LE pairing is not
ongoing before skipping the SDP. This uses the sequence of operations
where the LE LTK is generated first and link key is derived from the
LTK.

Test: mma -j32
Change-Id: Ife242c93c3adf90d581ac0bbf4896dd164b9f8e2