vsh: Fix warnings in command line completer

vsh: Fix warnings in command line completer

GCC complained that

vsh.c: In function 'vshReadlineOptionsGenerator':
vsh.c:2622:29: warning: unused variable 'opt' [-Wunused-variable]
         const vshCmdOptDef *opt = &cmd->opts[list_index];
                             ^
vsh.c: In function 'vshReadlineParse':
vsh.c:2830:44: warning: 'opt' may be used uninitialized in this function
[-Wmaybe-uninitialized]
             completed_list = opt->completer(autoCompleteOpaque,

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>