Rationale: current osmo-msc refactoring introduces RESET handling on IuCS.
In particular, it makes osmo-hnbgw be able to operate with an (upcoming)
osmo-msc that has strict RESET handling: it will send a RESET and require a
RESET ACK if it sees a new IuCS peer sending messages without prior RESET.
Even though a workaround to ignore missing RESET messages on IuCS will also be
in place in the new osmo-msc, this is a first small step towards more sane
RESET handling in osmo-hnbgw.
Related: OS#3820
Change-Id: I02bc74ef9fef61f4490b4d4dc3ce6c0a6d965909