global-functions: $WaitForFile: (mostly) revert changes

This (mostly) reverts commits 0e00a228d6
and e08bb2192d.

This is required for RouterOS 7.20beta4. It fixed recursive find for
files, and (still, or again?) suffers timing issues getting file
properties.

global-functions.rsc

@@ -1771,14 +1771,26 @@
   :global MAX;
 
   :set FileName [ $CleanFilePath $FileName ];
-  :local Delay ([ $MAX [ $EitherOr $WaitTime 2s ] 100ms ] / 10);
+  :local Delay ([ $MAX [ $EitherOr $WaitTime 2s ] 100ms ] / 9);
 
   :do {
-    :retry {
+    :retry { 
+      :if ([ :len [ /file/find where name=$FileName ] ] = 0) do={
+        :error false;
+      }
+    } delay=$Delay max=10;
+  } on-error={
+    :return false;
+  }
+
+  :while ([ :len [ /file/find where name=$FileName ] ] > 0) do={
+    :do {
       /file/get $FileName;
       :return true;
-    } delay=$Delay max=10;
-  } on-error={ }
+    } on-error={ }
+    :delay $Delay;
+    :set Delay ($Delay * 3 / 2);
+  }
 
   :return false;
 }