qcacmn: Hold lock while temporary deleting the connection entry

If two thread are trying to access the connection entry and one of them
Is modifying it by temporarily deleting an entry, the other thread may
get the invalid connection entry and decision made using that connection
table will be invalid.

Thus acquire the lock before the entry is temporarily deleted and release
only after its added back.

Change-Id: I83b9d7a77045d8bddd6cf3e4b1af80bded116e2f
CRs-Fixed: 2422611