sysmobts: Avoid memleak when multiple -c arguments are passed
sysmobts: Avoid memleak when multiple -c arguments are passed

Rely on optarg pointing to an address that will be valid for
the run of the entire application.

Fixes: CID 1206578

geosphere/osmo-bts,geosphere/osmo-bts,geosphere/osmo-bts,telenoobie/osmo-bts,telenoobie/osmo-bts,osmocom/osmo-bts,telenoobie/osmo-bts,telenoobie/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts,geosphere/osmo-bts