xe-cli completion: Hide COMPREPLY manipulation behind functions

Though the majority of completions were already using set_completions and the
like to add completion suggestions, there were two leftovers still needlessly
changing COMPREPLY themselves. This caused bugs, as in the case of

xe vm-import filename=<TAB>

autocompleting all of the filenames into the prompt instead of presenting
the choice. Let only these functions operate on COMPREPLY directly.

Signed-off-by: Andrii Sultanov <andrii.sultanov@cloud.com>

Author: Andrii Sultanov

ocaml/xe-cli/bash-completion

@@ -143,9 +143,9 @@ _xe()
                 IFS=$'\n,'
                 # Here we actually WANT file name completion, so using compgen is OK.
                 local comp_files=$(compgen -f "$value")
-                COMPREPLY=( "$comp_files" )
                 __xe_debug "triggering filename completion for the value:"
                 __xe_debug $(__tab_delimited_newline_array "$comp_files")
+                set_completions "$comp_files" "$value"
                 return 0
                 ;;
 
@@ -156,7 +156,6 @@ _xe()
                 if [ "${OLDSTYLE_WORDS[1]}" == "pif-reconfigure-ip" ]; then
                     IFS=$'\n,'
                     suggested_modes="dhcp,static,none"
-                    COMPREPLY=( $(compgen -W "dhcp ,static ,none" -- "$value") )
                 elif [ "${COMP_WORDS[1]}" == "pif-reconfigure-ipv6" ]; then
                     IFS=$'\n,'
                     suggested_modes="dhcp,static,none,autoconf"