Salt minion allow to specify HTTP backend

This is useful when using proxies. The default Tornado backend does not
utilize proxy environment variables and isn't able to set no_proxy variable.

Change-Id: I4a51c6fc9abe65d46ed4f3adeb30f7a25337857e
diff --git a/tests/pillar/minion_backend_urllib.sls b/tests/pillar/minion_backend_urllib.sls
new file mode 100644
index 0000000..6399b34
--- /dev/null
+++ b/tests/pillar/minion_backend_urllib.sls
@@ -0,0 +1,4 @@
+salt:
+  minion:
+    enabled: true
+    backend: urllib2