Fix deadlock in metastore

The interaction of continuous query service, the meta-store loading
and initializing raft state, and syncing node info could cause a
deadlock in some instances.  There was an extra read-lock taken by isLeader()
when it already had a read-lock.  Removing this extra lock fixes the startup
deadlock.

Fixes influxdata#3607

Fix metafile so it doesn't get trampled by other goroutines.

Fixes influxdata#3832 and fixes influxdata#3833

Ensure WAL cache gets sorted when needed.

Fixes influxdata#3792

Update CHANGELOG.md

Respond to OPTIONS requests on /query endpoint

Update admin assets for v0.9.2

Fixes authorization.

Adds GRANT and REVOKE statements for admin privilege. Adds authorization to the query endpoint.

Update CHANGELOG for PR 3217

[ci skip]

Copy latest packaging script to 0.9.1

Merge pull request influxdata#3146 from influxdb/snapshots-3014

Implement snapshots