Use an in-memory ccache to silence a compiler warning, for RT#6414.

Index: krb5-1.9.1/src/slave/kprop.c
===================================================================
--- krb5-1.9.1.orig/src/slave/kprop.c
+++ krb5-1.9.1/src/slave/kprop.c
@@ -188,9 +188,8 @@ void PRS(argc, argv)
 void get_tickets(context)
     krb5_context context;
 {
-    char   buf[BUFSIZ], *def_realm;
+    char buf[] = "MEMORY:_kproptkt", *def_realm;
     krb5_error_code retval;
-    static char tkstring[] = "/tmp/kproptktXXXXXX";
     krb5_keytab keytab = NULL;
 
     /*
@@ -229,11 +228,8 @@ void get_tickets(context)
 #endif
 
     /*
-     * Initialize cache file which we're going to be using
+     * Initialize an in-memory cache for temporary use
      */
-    (void) mktemp(tkstring);
-    snprintf(buf, sizeof(buf), "FILE:%s", tkstring);
-
     retval = krb5_cc_resolve(context, buf, &ccache);
     if (retval) {
         com_err(progname, retval, "while opening credential cache %s",