Remove unused imports in db migrations

I went on a hike through the migrations and decided to apply the boyscout rule.
Scouts honor.

Change-Id: I10c677cfd5186edce3ca96495eafc732168cac86

glance/db/sqlalchemy/migrate_repo/versions/003_add_disk_format.py

@@ -17,7 +17,6 @@
 
 from migrate.changeset import *
 from sqlalchemy import *
-from sqlalchemy.sql import and_, not_
 
 from glance.db.sqlalchemy.migrate_repo.schema import (
     Boolean, DateTime, Integer, String, Text, from_migration_import)

glance/db/sqlalchemy/migrate_repo/versions/004_add_checksum.py

@@ -17,7 +17,6 @@
 
 from migrate.changeset import *
 from sqlalchemy import *
-from sqlalchemy.sql import and_, not_
 
 from glance.db.sqlalchemy.migrate_repo.schema import (
     Boolean, DateTime, Integer, String, Text, from_migration_import)

glance/db/sqlalchemy/migrate_repo/versions/006_key_to_name.py

@@ -17,7 +17,6 @@
 
 from migrate.changeset import *
 from sqlalchemy import *
-from sqlalchemy.sql import and_, not_
 
 from glance.db.sqlalchemy.migrate_repo.schema import (
     Boolean, DateTime, Integer, String, Text, from_migration_import)

glance/db/sqlalchemy/migrate_repo/versions/007_add_owner.py

@@ -17,7 +17,6 @@
 
 from migrate.changeset import *
 from sqlalchemy import *
-from sqlalchemy.sql import and_, not_
 
 from glance.db.sqlalchemy.migrate_repo.schema import (
     Boolean, DateTime, BigInteger, Integer, String,

glance/db/sqlalchemy/migrate_repo/versions/008_add_image_members_table.py

@@ -19,8 +19,8 @@ from migrate.changeset import *
 from sqlalchemy import *
 
 from glance.db.sqlalchemy.migrate_repo.schema import (
-    Boolean, DateTime, BigInteger, Integer, String, Text,
-    create_tables, drop_tables, from_migration_import)
+    Boolean, DateTime, Integer, String, create_tables,
+    drop_tables, from_migration_import)
 
 
 def get_images_table(meta):

glance/db/sqlalchemy/migrate_repo/versions/009_add_mindisk_and_minram.py

@@ -17,7 +17,6 @@
 
 from migrate.changeset import *
 from sqlalchemy import *
-from sqlalchemy.sql import and_, not_
 
 from glance.db.sqlalchemy.migrate_repo.schema import (
     Boolean, DateTime, Integer, String, Text, from_migration_import)

glance/db/sqlalchemy/migrate_repo/versions/012_id_to_uuid.py

@@ -21,7 +21,6 @@ there are known issues with these libraries so SQLite and non-SQLite
 migrations must be done separately.
 """
 
-import copy
 import migrate
 import sqlalchemy