Establish data connection setting is stored per-SIM instead of per-modem

[Alfonso Sanchez-Beato]

The configuration data that makes ofono start a data connection is per-IMSI, that is, per SIM card. Concretely, it is stored in files of the form "/var/lib/ofono/<imsi_number>/gprs".

This is misleading for the user because she might do things like setting data connection off, and then insert a different SIM which "gprs" file says that data should be on, getting a data connection in the end.

Also, this is especially bad for dual-SIM, dual-standby modems where you might get to a situation where you try to data attach with both SIMs, which provokes a race condition, and in the end the user does not know which SIM is being used for data.

The solution would be to store that configuration data per modem, which are fixed and it is probably the way the user thinks when using system settings.