Always convert string type params to string

Schema.to_schema_type() should convert values passed to it to the
appropriate type.  So if the user passed a version number of 9.4 and
they defined it in the template with a string type, we should get the
string '9.4' back, instead of the error "The value '9.4' is invalid for
type 'string'".

Co-Authored-By: Richard Lee <rblee88@gmail.com>
Closes-Bug: #1353701
Change-Id: If7abd129dc7819c6ac01f9bf7dfdbe397ec09c65
Merge "Always convert string type params to string"