tidb-operator v1.0.0-beta.1-p2

This release still focuses on stability. See the detailed release notes below:

• new algorithm for scheduler HA predicate (#260)
• add tidb discovery service (#262)
• serial scheduling (#266)
• change tolerations type to an array (#271)
• start directly when where is join file (#275)
• add code coverage icon (#272)
• in values.yml, omit just the empty leaves (#273)
• charts: backup to ceph object storage (#280)
• add ClusterIDLabelKey label to TidbCluster (#279)