ktest: Fix tar extracting of modules to target

The tar command to create the module directory is cjf, but the
extraction only had xf. This works on most versions of tar, but some
versions of tar require xjf for extraction as well.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

tools/testing/ktest/ktest.pl

@@ -1087,7 +1087,7 @@ sub install {
 
     unlink "$tmpdir/$modtar";
 
-    run_ssh "'(cd / && tar xf /tmp/$modtar)'" or
+    run_ssh "'(cd / && tar xjf /tmp/$modtar)'" or
 	dodie "failed to tar modules";
 
     run_ssh "rm -f /tmp/$modtar";