rollback mysql driver

this go-sql-driver/mysql#302 seems to have pretty much
crippled the ability to use mysql, so we need to lock a version before that
until that issue gets fixed.

Author: Reed Allman

glide.lock

@@ -44,6 +44,7 @@ import:
 - package: github.com/go-openapi/swag
 - package: github.com/go-openapi/validate
 - package: github.com/go-sql-driver/mysql
+  version: 21d7e97c9f760ca685a01ecea202e1c84276daa1
 - package: github.com/google/btree
 - package: github.com/iron-io/iron_go3
   subpackages: