floss: serialize HoGP and DIS

When preparing to connect HoGP profile, the following two activities
are started simultaneously.
(1) discovery of HoGP service, including register for notification
(2) discovery of DIS

In (1) we have an interop MULTIPLE_HOGP_SERVICE_CHOOSE_THIRD which
actually needs (2) to be done first. Therefore, logically the two
activities above must not run simultaneously.

Bug: 357011645
Test: m -j
Test: Verify Logitech Casa Touch is pairable and usable
Flag: EXEMPT, floss only
Change-Id: I26767f1762b7791c3142dccac5bda3819bd7c5d1