xapi-tools: fixes cache cleaner script

Fixes cache cleaner script by removing import of
driver and using session directly to call vm_utils.

There is no test included for this. Since this is out of nova
tree, adding tests is tracked in 1481705

Closes-Bug: #1481693

Change-Id: I25ee22777baecaf64de63a39d19e8f8f514f70b3

Author: sulochan

tools/xenserver/destroy_cached_images.py

@@ -29,7 +29,7 @@
 
 from nova import config
 from nova import utils
-from nova.virt.xenapi import driver as xenapi_driver
+from nova.virt.xenapi.client import session
 from nova.virt.xenapi import vm_utils
 
 destroy_opts = [
@@ -45,18 +45,26 @@
 CONF = cfg.CONF
 CONF.register_cli_opts(destroy_opts)
 
+CONF.import_opt('connection_url', 'nova.virt.xenapi.driver',
+                group='xenserver')
+CONF.import_opt('connection_username', 'nova.virt.xenapi.driver',
+                group='xenserver')
+CONF.import_opt('connection_password', 'nova.virt.xenapi.driver',
+                group='xenserver')
+
 
 def main():
     config.parse_args(sys.argv)
     utils.monkey_patch()
 
-    xenapi = xenapi_driver.XenAPIDriver()
-    session = xenapi._session
+    _session = session.XenAPISession(CONF.xenserver.connection_url,
+                                     CONF.xenserver.connection_username,
+                                     CONF.xenserver.connection_password)
 
-    sr_ref = vm_utils.safe_find_sr(session)
+    sr_ref = vm_utils.safe_find_sr(_session)
     destroyed = vm_utils.destroy_cached_images(
-            session, sr_ref, all_cached=CONF.all_cached,
-            dry_run=CONF.dry_run)
+        _session, sr_ref, all_cached=CONF.all_cached,
+        dry_run=CONF.dry_run)
 
     if '--verbose' in sys.argv:
         print '\n'.join(destroyed)