mtr is checking the wrong path for the embedded executable
on out of tree builds.
The is_embedded.inc tests are also checking the version rather
than the MTR MYSQL_EMBEDDED environment variable.
As a result, a few tests are out of date in the result recordings.
- Remove the "hack" from mtr.pl that skipped searching for the .dll files
when embedded and windows. Now the variables will be preoperly initialized.
- Make the tests detect that they can't run on windows+embedded
