Changing DB engine value

The patch chnages DB engine value from mysql+pymsql
to mysql in order arrange the value and to be used in
templates, other configuration snippet, etc. like other
salt-formulas have.

Change-Id: Ib826014bcd0941707baa5a609302202d3b1cc941
diff --git a/metadata/service/server/single.yml b/metadata/service/server/single.yml
index 68fc4c1..c1e9322 100644
--- a/metadata/service/server/single.yml
+++ b/metadata/service/server/single.yml
@@ -14,7 +14,7 @@
       version: ${_param:aodh_version}
       ttl: 86400
       database:
-        engine: "mysql+pymysql"
+        engine: "mysql"
         host: ${_param:single_address}
         port: 3306
         name: aodh