When RDS is deleted, its status is not correctly tracked

[RaitoBezarius]

It seems like when RDS is deleted that the code checking for its status has some bug that makes it "instantly marked as deleted", whereas it's in fact in deletion (I could see on the RDS management console that an instance was currently in deletion), this, of course, create problems when you have some resources which cannot be deleted before the RDS is deleted (DB Subnets for example!).

I'll try to send a PR to fix this.