Clean up lock module dependencies

[mgao0]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

Current ivy file and pom.xml in helix-lock module contain some unnecessary dependencies. This PR cleans up these dependencies.

Description

• Here are some details about my PR, including screenshots of any UI changes:

Removed snakeyaml from ivy file.
Removed snakeyaml, commons-lang3, httpclient, xstream from pom.xml

Tests

• The following is the result of the "mvn test" command on the appropriate module:
  helix-lock module
  [INFO] Results:
  [INFO]
  [INFO] Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
  [INFO]
  [INFO] ------------------------------------------------------------------------
  [INFO] BUILD SUCCESS
  [INFO] ------------------------------------------------------------------------
  [INFO] Total time: 01:23 min
  [INFO] Finished at: 2020-05-29T11:50:59-07:00
  [INFO] ------------------------------------------------------------------------

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

• My diff has been formatted using helix-style.xml
  (helix-style-intellij.xml if IntelliJ IDE is used)

[mgao0]

This PR is ready to be merged, approved by @narendly.