stash-cache: allow environment variable override of redirector (SOFTWARE-5641)

Author: matyasselmeci

configs/stash-cache/config.d/40-stash-cache-plugin.cfg

@@ -58,6 +58,12 @@ else
    pss.setopt ConnectionRetry 2
 fi
 
+# Allow environment variable override of redirector
+if defined ?~XC_REDIRECTOR
+   set eREDIRECTOR=$XC_REDIRECTOR
+   pss.origin $eREDIRECTOR
+fi
+
 # Cache plugin parameters
 #
 # The default values here should be sufficient for most use cases. To change them, override them