[atServer] Correct Coverity detected issues
[atServer] Correct Coverity detected issues

Resolves: LE-6881
Change-Id: Ic6f168fd407161e2fbef84fb665d1ff69efbb904

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