use colon as nullcommand instead of dummy statement

releng/inc/releng_getopts.inc

@@ -122,8 +122,7 @@ next_is=
 for i in "$@"
 do
   if test "$next_is" = "ignore"
-  then
-       dummy=dummy
+  then :
   elif test "$next_is" = "x"
   then
        RELENG_XORRISO="$i"

releng/manual_devices

@@ -148,8 +148,7 @@ case ${RET} in
       get_devices "$devices" "$dev"
       RET="$?"
       if test "$RET" = 0
-      then
-           dummy=dummy
+      then :
       else
            echo "FAIL : ${SELF} : Device scan or single drive listing failed"
            exit "$RET"

releng/run_all_releng

@@ -29,8 +29,7 @@ next_is=
 for i in "$@"
 do
   if test "$next_is" = "ignore"
-  then
-       dummy=dummy
+  then :
   elif test "$next_is" = "x"
   then
        RELENG_XORRISO="$i"