Rename XHPAST database
Summary: Rename the XHPAST database from {$NAMESPACE}_xpastview to {$NAMESPACE}_xhpast.
Test Plan: Ran ./bin/storage --namespace test upgrade --no-quickstart.
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D14442