SM: Refine channel connect logic

If the ACL is active then we just hold the ACL on connect instead of attempting to reconnect ACL.

Bug: 145638034
Test: cert/run --host --test_filter=SecurityTest
Test: atest --host bluetooth_test_gd:SecurtityManagerChannel
Tag: #gd-refactor
Change-Id: I895ccb1bc4f81caf45e95703706f4a0b66eb93bf