Call create_database on correct object

MSP-9106

create_database is defined on `ActiveRecord::Base#connection`, not
`ActiveRecord::Base` directly.  The specs didn't catch this because
creating a database has to be done with should_receives and stubs.  The
error was detected by doing `rake db:drop` and allowing `msfconsole` to
try to create the database.
Merge branch 'limhoff-r7/bug/create_database' into HEAD