Correct MySQL jdbcUrl format

The MySQL JDBC driver will not accept `jdbcUrl` produced by the broker. The correct format is:
`jdbc:mysql://[host][,failoverhost...][:port]/[database][?propertyName1][=propertyValue1]...`
quoting http://dev.mysql.com/doc/connector-j/en/connector-j-reference-configuration-properties.html

Sample error:
```
2014-09-29T21:01:24.63+0000 [App/0]   OUT Caused by: java.lang.NumberFormatException: For input string: "rqzUzkIxACpoKQup@10.0.1.61:3306"
"p-mysql": [
    {
      "name": "mysql-1",
      "label": "p-mysql",
      "tags": [
        "mysql"
      ],
      "plan": "100mb-dev",
      "credentials": {
        "hostname": "10.0.1.61",
        "port": 3306,
        "name": "cf_4840c037_d78f_4dcf_9a7b_7d1b9fc08e80",
        "username": "H4iJMTnrtW7zdx5m",
        "password": "rqzUzkIxACpoKQup",
        "uri": "mysql://H4iJMTnrtW7zdx5m:rqzUzkIxACpoKQup@10.0.1.61:3306/cf_4840c037_d78f_4dcf_9a7b_7d1b9fc08e80?reconnect=true",
        "jdbcUrl": "jdbc:mysql://H4iJMTnrtW7zdx5m:rqzUzkIxACpoKQup@10.0.1.61:3306/cf_4840c037_d78f_4dcf_9a7b_7d1b9fc08e80"
      }
    }
  ],
```