[layer23] Fixed cell search process of automatic network selection

[layer23] Fixed cell search process of automatic network selection

If there is no (more) "PLMN in list", a complete search is triggered, so
all available cells are searched. Then the list of available networks is
tried for location updating (if allowed) in a defined order. If the
list is done, the process searches for all available cells again.

Note: The process will cause location updating on all networks until all
networks have rejected the mobile or if one network allowed the location
updating. To prevent this, use manual network selection, and set 'rplmn' of
test-sim, so only location updating is tried on the RPLMN.