* Increase the default snapshot timeout. The timeout is not currently
  configurable from Rancher, and larger clusters are frequently seeing
  uploads fail at 30 seconds.
* Enable compression for scheduled snapshots if enabled on the
  command-line. The CLI flag was not being passed into the etcd config.
* Only set the S3 content-type to application/zip if the file is zipped.
* Don't run more than one snapshot at once, to prevent misconfigured
  etcd snapshot cron schedules from stacking up.
Signed-off-by: Brad Davidson <brad.davidson@rancher.com>