Do not rename primary key index when renaming table

When the migrator renames a table, for example for upgrade simulation,
it should not rename the primary key to avoid messing up with the diff
because the MySQL Doctrine code expects that index to always be called
"primary".
Added unit test for checkMigrate with primary key + autoinc

Added unit test to make sure that checkMigrate() works when adding a
primary key and autoincrement column to a table schema.
Merge pull request #9065 from owncloud/migrator-keepprimaryindexname

Do not rename primary key index when renaming table