Change useexisting to extend_existing to fix deprecation warnings.

This squelches a deprecation warning during installation.

We're already using extend_existing in other places, so I don't
think this causes any new version compatibility issues.

Fixes bug 925609.  (Already marked fixed, but this hits more cases.)

Includes some merges with a whitespace-cleanup fix.

Change-Id: Ia166e9184ed3e13753c5669a1006a3711738319a

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

@@ -50,7 +50,7 @@ def get_images_table(meta):
                           default=False,
                           index=True),
                    mysql_engine='InnoDB',
-                   useexisting=True)
+                   extend_existing=True)
 
     return images
 

glance/db/sqlalchemy/migrate_repo/versions/005_size_big_integer.py

@@ -51,7 +51,7 @@ def get_images_table(meta):
                           default=False,
                           index=True),
                    mysql_engine='InnoDB',
-                   useexisting=True)
+                   extend_existing=True)
 
     return images
 

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

@@ -66,7 +66,7 @@ def get_image_properties_table(meta):
                                     index=True),
                              UniqueConstraint('image_id', 'name'),
                              mysql_engine='InnoDB',
-                             useexisting=True)
+                             extend_existing=True)
 
     return image_properties