api: add replication status to region

[disksing]

Signed-off-by: disksing [email protected]

What problem does this PR solve?

Fix #2338

What is changed and how it works?

./bin/pd-ctl region
{"count":1,"regions":[{"id":2,"start_key":"","end_key":"","epoch":{"conf_ver":1,"version":1},"peers":[{"id":3,"store_id":1}],"leader":{"id":3,"store_id":1},"written_bytes":41,"read_bytes":0,"written_keys":1,"read_keys":0,"approximate_size":1,"approximate_keys":0,"replication_status":{"state":"INTEGRITY_OVER_LABEL","state_id":4}}]}

Check List

Tests

• Manual test (add detailed scripts or steps below)
  • start cluster with replication mode and query region

Code changes

• Has HTTP API interfaces change (Don't forget to update API document)

[disksing]

/merge

[sre-bot]

/run-all-tests

[sre-bot]

@disksing merge failed.

[disksing]

travis CI env problem, merging.