floss: Scanner: Ensure the MSFT enable state correct

inband_msft_adv_monitor_enable_callback should make sure the scanner end
up in a correct MSFT enable state. However it missed a case that the
scanner could be changed when MSFT enable is pending.

Bug: 392975255
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: Run CTSV LE client test, verify each Start/StopScan triggers
      MSFT Enable
Flag: EXEMPT, Floss-only change
Change-Id: I19152a7e5e5422dcc528d8ae6508aa7d2fc68579