[atServer] Fix strncpy with wrong max size
[atServer] Fix strncpy with wrong max size

Resolves: LE-13039
Change-Id: I95e4335b7fdec0e812c4d7824efd150b064d88d8

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