Add charset and engine settings to every table

Each MySQL table requires setting a default charset and engine,
otherwise default values are used. It all worked previously because
migration scripts enforce those values to the correct ones. Since
we want to be able to generate the schema from models, those MySQL
specific parameters must be set.

This patch reuses a table_args() function that is already defined.

Closes-bug: #1351431
Change-Id: I3dafed9dfe5042fab1cff2ea029ea62c5e5cbea3
Merge "Add charset and engine settings to every table"