bitbake: toaster: Make 0021 migration compatible with MySQL

Two issues prevent this migration from working correctly
with a MySQL back-end:

1. MySQL won't allow a default value to be set for an
AutoField, which is what the migration tries to do
for project_id ("ValueError: The database backend does not accept
0 as a value for AutoField.")

2. When migrations are applied to a MySQL back-end, Django
(via South) attempts a dry run of the migration first: it
applies the forward migration then rolls it back. However, this
migration raises an exception on roll back, which causes the
whole series of migrations to fail.

This commit fixes both issues.

[YOCTO #7932]

(Bitbake rev: 12f6278d56d7dec57308adc17411802f15d395d7)

Signed-off-by: Elliot Smith <elliot.smith@intel.com>
Signed-off-by: brian avery <avery.brian@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/orm/migrations/0021_auto__chg_field_build_project__chg_field_project_bitbake_version__chg_.py

@@ -7,10 +7,12 @@ from django.db import models
 
 class Migration(SchemaMigration):
 
+    no_dry_run = True
+
     def forwards(self, orm):
 
         # Changing field 'Build.project'
-        db.alter_column(u'orm_build', 'project_id', self.gf('django.db.models.fields.related.ForeignKey')(default=0, to=orm['orm.Project']))
+        db.alter_column(u'orm_build', 'project_id', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['orm.Project']))
 
         # Changing field 'Project.bitbake_version'
         db.alter_column(u'orm_project', 'bitbake_version_id', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['orm.BitbakeVersion'], null=True))