db: fixing column alias in create_views.sql

This patch fixes and issue caused by patch http://gerrit.ovirt.org/#/c/25880
in create_views.sql on line 779. Instead of

  vds_statistics.boot_time

there should be

  vds_statistics.boot_time as boot_time

Change-Id: Ia4e0094b1488f7fc452dc9c34bf9f6906a5a22ac
Signed-off-by: Eli Mesika <emesika@redhat.com>