src: Use EF_OPL to check roaming status

Some operators (MVNOs, or Orange/T_Mobile UK case) store in EF_OPL
their home networks, so we remove the roaming flag if the network we
are registered in is present in the file. Although this is not strictly
conformant with the standard, seems to be common practive among
operators, as no operator would care about changing the displayed name
for a network which is not among its home networks (EF_OPL stores the
index for the EF_PNN entry for a PLMN).
test: Adapt test scripts to multi-sim scenarios

Some tests scripts were not ready to handle situations with more than
one modem present. This changes fixes some of the scripts, including
those used in the test plan.
Merge pull request #88 from alfonsosanchezbeato/test-multisim

Adapt test scripts to multi-sim scenarios
Merge pull request #86 from alfonsosanchezbeato/roaming-opl

Use EF_OPL to check roaming status