Bug #38807 schema default collation is not correctly applied on contained tables

Description:
when collation of a  table is set to "schema default" this is not correctly applied when synching 

How to repeat:
- create a schema using utf8_czech_ci as collation for schema
- create a table (at least one PK col)
- Forward engineer this to a DB -> collation is correctly set (for tables and schema itself)
- sync the schema against the same DB again -> now WB wants to ALTER the tables collation back to 'utf8_general_ci' 

Suggested fix:
don't alter/reset collation if the user didn't change it

this has been fixed in repository and will be included in 5.2.7

An entry has been added to the 5.2.7 changelog:

If a collation was set as the schema default, this was not correctly handled when the model was synchronized with a live database.

If a collation was set as a schema default, and then the model forward engineered to a database, then the collation was correctly set. If however, the model was then synchronized with the live database, MySQL Workbench attempted to alter the collations to utf8_general_ci.