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
