Werk #13353: Linux agent: Fix two localisation issues

On some systems, the linux agent tried to set invalid localisation settings. For example, when C.utf8 is not available, but es_EC.utf8 is, the agent still tried to set C.utf8 as localisation, which resulted in the error setlocale: LC_ALL: cannot change locale.

Furthermore, in the rare case where the locale or the inpath command were not available, no localisation was set. These cases now default to LC_ALL=C.

To the list of all Werks