Remove the stale puma pidfile before starting the server process

[ajay-vel]

Desired Outcome

• This changes ensures that the stale pidfile is removed before starting the conjur server process
  This issue addresses Docker container fails to restart #2381

Implemented Changes

• A new method is added to conjur-cli to check if the stale puma pid file exists and deletes it if it exists.

Connected Issue/Story

• Issue Docker container fails to restart #2381

Definition of Done

• A new method checks if the stale pidfile exists and it is removed before the starting the conjur server.

Changelog

• The CHANGELOG has been updated with the bug that was fixed.

Test coverage

• This PR includes two new unit tests to go with the code
  changes

Documentation

• This PR does not require updating any documentation

Behavior

• No behavior was changed with this PR

Security

• There are no security aspects to these changes

[micahlee]

Hey @ajay-vel , another thing I just realized is that this PR description is not the standard template. Can you please use that instead?

There are some important questions there for both you and the reviewer to consider for each PR. For example, this change does need entry in the CHANGELOG.

Thanks!

### Desired Outcome

*Please describe the desired outcome for this PR.  Said another way, what was
the original request that resulted in these code changes?  Feel free to copy
this information from the connected issue.*

### Implemented Changes

*Describe how the desired outcome above has been achieved with this PR. In
particular, consider:*

- _What's changed? Why were these changes made?_
- _How should the reviewer approach this PR, especially if manual tests are required?_
- _Are there relevant screenshots you can add to the PR description?_

### Connected Issue/Story

Resolves #[relevant GitHub issue(s), e.g. 76]

CyberArk internal issue link: [insert issue ID]()

### Definition of Done
*At least 1 todo must be completed in the sections below for the PR to be
merged.*

#### Changelog

- [ ] The CHANGELOG has been updated, or
- [ ] This PR does not include user-facing changes and doesn't require a
  CHANGELOG update

#### Test coverage

- [ ] This PR includes new unit and integration tests to go with the code
  changes, or
- [ ] The changes in this PR do not require tests

#### Documentation

- [ ] Docs (e.g. `README`s) were updated in this PR
- [ ] A follow-up issue to update official docs has been filed here: [insert issue ID]()
- [ ] This PR does not require updating any documentation

#### Behavior

- [ ] This PR changes product behavior and has been reviewed by a PO, or
- [ ] These changes are part of a larger initiative that will be reviewed later, or
- [ ] No behavior was changed with this PR

#### Security

- [ ] Security architect has reviewed the changes in this PR,
- [ ] These changes are part of a larger initiative with a separate security review, or
- [ ] There are no security aspects to these changes 

[micahlee]

One other thing I remembered seeing the PR checklist again is that we should add tests for this change. They can probably go in the existing spec suite here: https://github.com/cyberark/conjur/blob/master/spec/conjurctl/server_spec.rb

We should verify the behavior:

• when the PID file does exist
• when the PID file does not exist

[micahlee]

Hey @ajay-vel , thanks for updating the tests! One last comment on the changelog, and this should be good to go!

[codeclimate]

Trailing spaces

[codeclimate]

Code Climate has analyzed commit 80fe998 and detected 2 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Style	2

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 87.9% (-1.3% change).

View more on Code Climate.

[micahlee]

LGTM, thanks for the effort getting this wrapped up!