[review] Retry reloads for the Band/Mode set operation

[Aleksander Morgado]

Hey!

The following MR adds some retry mechanism to the "reloading" of
bands/modes during a set operation.

https://gitlab.freedesktop.org/mobile-broadband/ModemManager/merge_requests/130

E.g. if we were configured with band "EUTRAN 19" and we try to set
"EUTRAN 20" instead, the modem may return a successful reply to the
band change request, but if we read the current bands right away it
could still return the previous "EUTRAN 19" and not the new "EUTRAN
20" we're trying to set. Given that the current bands are only loaded
after the set operation, this would mean that we return a successful
response to the user that called SetCurrentBands(), but the actual
CurrentBands reported are the previous ones before the set. This is
easily reproducible on QMI modems using "NAS Set System Selection
Preference.

-- 
Aleksander
https://aleksander.es