resolveDatabase is not working if database is changed using USE

[ajnavarro]

related: #805

We need to handle database change on resolveDatabase rule. Right now is only resolving the current database.

[erizocosmico]

Can you provide a reproduction case for this? As far as I can see this behaviour is tested and working properly: https://github.com/src-d/go-mysql-server/blob/master/engine_test.go#L2657-L2672

[ajnavarro]

I did some tests and I'm not able to reproduce the error anymore.