[kmod] Trim excessive token in program name
[kmod] Trim excessive token in program name

Legato appends the instance number of an app in the app's program
name. E.g. "kmod@0". The part of "@0" will be shown in the output
of `kmod --help`, which could be misleading.
A simple string manipulation can fix this problem and avoid
changing the real program name.

Resolves: LE-12282
Change-Id: I5b66549f9446bdefd7af5ce75dc3224d4aa0e9d3

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af