ctrl: f_counter_name_vals_get_n(): add start_idx, for hnbgw

Allow starting with a specific 'msc' / 'sgsn' instance without having to
read all the lower numbers along. For HNBGW_Tests.ttcn.

Change-Id: I9b74a1df9e115883b4b0ac0f606a370c6aca7f40
1 file changed