Accept yes/no for boolean environment variables (#2893)

scripts/start-utils

@@ -64,7 +64,7 @@ function getFilenameFromUrl() {
 
 function isTrue() {
   case "${1,,}" in
-  true | on | 1)
+  true | yes | on | 1)
     return 0
     ;;
   *)
@@ -75,7 +75,7 @@ function isTrue() {
 
 function isFalse() {
   case "${1,,}" in
-  false | off | 0)
+  false | no | off | 0)
     return 0
     ;;
   *)
@@ -345,4 +345,4 @@ function ensureRemoveAllModsOff() {
     log "WARNING using REMOVE_OLDS_MODS interferes with $reason -- it is now disabled"
     REMOVE_OLD_MODS=false
   fi
-}
+}