Don't ignore encryption change events while in IDLE state

If we hit an LMP timeout, we may have pending security operations while
in the IDLE state. If we then get an encryption change event while in
IDLE, we should handle it, as otherwise these security operations will
be unhandled.

Test: manual
Bug: 267672620
Change-Id: I61c6eb5bd72ba6c3dac1186de1b893e5b461e368