tab completors: be quiet even if the which command would like to complain

if `which` thought there was an error, some ugly error messages were
printed when pressing the tabulator key. note that this probably obly
affected people who used this as the default completor...

etc/opm_bash_completion.sh.in

@@ -11,7 +11,7 @@ _ewoms_parameter_completor()
 
     cmd="${COMP_WORDS[0]}"
     cur="${COMP_WORDS[COMP_CWORD]}"
-    fullcmd="$(which "$cmd")"
+    fullcmd="$(which "$cmd" 2> /dev/null)"
     ALL_OPTS=$("$fullcmd" --help 2> /dev/null | grep '^ *--' | sed 's/ *\(--[a-zA-Z0-9\-]*\)=.*/\1=/')
     ALL_OPTS=$(echo "$ALL_OPTS" | sed 's/^ *--help.*/--help/')
     COMPREPLY=( $(compgen -A file -W "$ALL_OPTS" -- "${cur}") )
@@ -32,7 +32,7 @@ _ewoms_generic_parameter_completor()
     cmd="${COMP_WORDS[0]}"
     cur="${COMP_WORDS[COMP_CWORD]}"
 
-    fullcmd="$(which "$cmd")"
+    fullcmd="$(which "$cmd" 2> /dev/null)"
     if test -z "$fullcmd" || \
        ! test -x "$fullcmd" || \
        (! test -f "$fullcmd" && ! test -h "$fullcmd" ) || \