shardddl: add infoOpLock for pessmist shardddl (#1257)

[ti-srebot]

cherry-pick #1257 to release-2.0

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What problem does this PR solve?

close #1253

[2020-10-30T02:25:09.879Z] [2020/10/30 10:24:51.715 +08:00] [INFO] [pessimist.go:522] ["the lock for the shard DDL lock operation has been resolved"] [component="shard DDL pessimist"] [operation="{\"id\":\"test-`shardddl`.`tb`\",\"task\":\"test\",\"source\":\"mysql-replica-02\",\"ddls\":[\"ALTER TABLE `shardddl`.`tb` ADD UNIQUE `idx_a`(`a`)\"],\"exec\":false,\"done\":true}"]
[2020-10-30T02:25:09.879Z] [2020/10/30 10:24:51.818 +08:00] [INFO] [pessimist.go:466] ["receive a shard DDL info"] [component="shard DDL pessimist"] [info="{\"task\":\"test\",\"source\":\"mysql-replica-01\",\"schema\":\"shardddl\",\"table\":\"tb\",\"ddls\":[\"ALTER TABLE `shardddl`.`tb` ADD UNIQUE `idx_b`(`b`)\"]}"]
[2020-10-30T02:25:09.880Z] [2020/10/30 10:24:51.818 +08:00] [ERROR] [pessimist.go:472] ["fail to try sync shard DDL lock"] [component="shard DDL pessimist"] [info="{\"task\":\"test\",\"source\":\"mysql-replica-01\",\"schema\":\"shardddl\",\"table\":\"tb\",\"ddls\":[\"ALTER TABLE `shardddl`.`tb` ADD UNIQUE `idx_b`(`b`)\"]}"] [error="[code=38016:class=dm-master:scope=internal:level=high], Message: sharding ddls in ddl lock [ALTER TABLE `shardddl`.`tb` ADD UNIQUE `idx_a`(`a`)] is different with [ALTER TABLE `shardddl`.`tb` ADD UNIQUE `idx_b`(`b`)], Workaround: Please use show-ddl-locks command for more details."]
[2020-10-30T02:25:09.880Z] [2020/10/30 10:24:51.828 +08:00] [INFO] [pessimist.go:652] ["delete shard DDL lock operations"] [component="shard DDL pessimist"] [lock=test-`shardddl`.`tb`] [revision=114]

we have fixed put shard DDL info if the done operation exists in #725 , so the above log may because the done operations have been deleted but lock has not.

What is changed and how it works?

add mutex in handleInfoPut and handleOperationPut

Check List

Tests

• Integration test

[csuzhangxc]

LGTM