The value of tmnxMobPdnApnChrgCcIgnoreRoaming specifies to ignore
HSS or MME supplied charging characteristics for roaming scenarios.
Corresponding default profile is selected when the received charging
characteristics is ignored.
When the value of tmnxMobPdnApnChrgCcIgnoreRoaming is 'inherit', the
value is inherited from the value of tmnxMobPdnChrgCcIgnoreRoaming
which specifies to ignore HSS or MME supplied charging characteristics
for roaming scenarios at the gateway level.