show cli flags in logs (#1807)

[sre-bot]

cherry-pick #1807 to release-1.1

---

What problem does this PR solve?

this is useful in debugging. in addition to component version, we can know CLI flags from logs.

example logs of tidb-controller-manager:

I0227 17:36:49.969981   88390 version.go:38] Welcome to TiDB Operator.
I0227 17:36:49.970745   88390 version.go:39] TiDB Operator Version: version.Info{GitVersion:"v1.1.0-beta.1.97+89e0c38525404a", GitCommit:"89e0c38525404aea9c085a64848ad36bcbcd8bf1", GitTreeState:"clean", BuildDate:"2020-02-27T09:36:35Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
I0227 17:36:49.970794   88390 main.go:97] FLAG: --V="false"
I0227 17:36:49.970805   88390 main.go:97] FLAG: --add_dir_header="false"
I0227 17:36:49.970809   88390 main.go:97] FLAG: --alsologtostderr="false"
I0227 17:36:49.970814   88390 main.go:97] FLAG: --auto-failover="true"
I0227 17:36:49.970817   88390 main.go:97] FLAG: --cluster-scoped="true"
I0227 17:36:49.970827   88390 main.go:97] FLAG: --features="AdvancedStatefulSet=false,AutoScaling=false,StableScheduling=true"
I0227 17:36:49.970859   88390 main.go:97] FLAG: --log_backtrace_at=":0"
I0227 17:36:49.970867   88390 main.go:97] FLAG: --log_dir=""
I0227 17:36:49.970871   88390 main.go:97] FLAG: --log_file=""
I0227 17:36:49.970878   88390 main.go:97] FLAG: --log_file_max_size="1800"
I0227 17:36:49.970882   88390 main.go:97] FLAG: --logtostderr="true"
I0227 17:36:49.970895   88390 main.go:97] FLAG: --pd-failover-period="5m0s"
I0227 17:36:49.970899   88390 main.go:97] FLAG: --pod-webhook-enabled="false"
I0227 17:36:49.970903   88390 main.go:97] FLAG: --resync-duration="30s"
I0227 17:36:49.970906   88390 main.go:97] FLAG: --skip_headers="false"
I0227 17:36:49.970909   88390 main.go:97] FLAG: --skip_log_headers="false"
I0227 17:36:49.970919   88390 main.go:97] FLAG: --stderrthreshold="2"
I0227 17:36:49.970943   88390 main.go:97] FLAG: --test-mode="false"
I0227 17:36:49.970948   88390 main.go:97] FLAG: --tidb-backup-manager-image="pingcap/tidb-backup-manager:latest"
I0227 17:36:49.970952   88390 main.go:97] FLAG: --tidb-discovery-image="pingcap/tidb-operator:latest"
I0227 17:36:49.970955   88390 main.go:97] FLAG: --tidb-failover-period="5m0s"
I0227 17:36:49.970958   88390 main.go:97] FLAG: --tikv-failover-period="5m0s"
I0227 17:36:49.970960   88390 main.go:97] FLAG: --v="1"
I0227 17:36:49.970970   88390 main.go:97] FLAG: --version="false"
I0227 17:36:49.970973   88390 main.go:97] FLAG: --vmodule=""
I0227 17:36:49.970977   88390 main.go:97] FLAG: --workers="5"

What is changed and how does it work?

Check List

Tests

• Unit test
• E2E test
• Stability test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has Go code change
• Has CI related scripts change
• Has Terraform scripts change

Side effects

• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Does this PR introduce a user-facing change?:

NONE

[weekface]

LGTM

[Yisaer]

/run-e2e-in-kind

[cofyc]

/merge

[sre-bot]

Your auto merge job has been accepted, waiting for 1824

[sre-bot]

/run-all-tests

[sre-bot]

@sre-bot merge failed.

[cofyc]

/merge

[sre-bot]

Your auto merge job has been accepted, waiting for 1831

[Yisaer]

/run-e2e-in-kind