SUBMARINE-711. Add committer info in git commit log

### What is this PR for?

Add committer info in the git commit log

### What type of PR is it?
[Improvement]

### Todos
* [ ] - Task

### What is the Jira issue?
* Open an issue on Jira https://issues.apache.org/jira/browse/SUBMARINE-711

### How should this be tested?
* First time? Setup Travis CI as described on https://submarine.apache.org/contribution/contributions.html#continuous-integration
* Strongly recommended: add automated unit tests for any new or changed behavior
* Outline any manual steps to test the PR here.

### Screenshots (if appropriate)

### Questions:
* Does the licenses files need update? Yes/No
* Is there breaking changes for older versions? Yes/No
* Does this needs documentation? Yes/No

Author: Kent Yao <yao@apache.org>

Closes #493 from yaooqinn/SUBMARINE-711 and squashes the following commits:

3d50ac0 [Kent Yao] newline
ce1b98c [Kent Yao] a Signed-off-by: Kent Yao<yao@apache.org>
diff --git a/dev-support/cicd/merge_submarine_pr.py b/dev-support/cicd/merge_submarine_pr.py
index 7b5e57c..5a8c3b7 100755
--- a/dev-support/cicd/merge_submarine_pr.py
+++ b/dev-support/cicd/merge_submarine_pr.py
@@ -143,9 +143,11 @@
 
     merge_message_flags += ["-m", authors]
 
+    committer_name = run_cmd("git config --get user.name").strip()
+    committer_email = run_cmd("git config --get user.email").strip()
+    merge_message_flags += ["-m", "\n" + "Signed-off-by: %s <%s>" % (committer_name, committer_email)]
+
     if had_conflicts:
-        committer_name = run_cmd("git config --get user.name").strip()
-        committer_email = run_cmd("git config --get user.email").strip()
         message = "This patch had conflicts when merged, resolved by\nCommitter: %s <%s>" % (
             committer_name, committer_email)
         merge_message_flags += ["-m", message]