Add deployment_type of Jira server in `jira_tracker_data` table"

What does this MR do?

Add deployment_type enum column to jira_tracker_data table (and corresponding enum values).

This will allow us to capture what type of Jira server is being used, and use the appropriate API.

Database

rake db:migrate

> rake db:migrate
== 20200715171155 AddDeploymentTypeToTracker: migrating =======================
-- add_column(:jira_tracker_data, :deployment_type, :smallint, {:default=>0, :allow_null=>false})
   -> 0.0119s
== 20200715171155 AddDeploymentTypeToTracker: migrated (0.0121s) ==============

rake db:rollback

> rake db:rollback
== 20200715171155 AddDeploymentTypeToTracker: reverting =======================
-- remove_column(:jira_tracker_data, :deployment_type, :smallint, {:default=>0, :allow_null=>false})
   -> 0.0099s
== 20200715171155 AddDeploymentTypeToTracker: reverted (0.0128s) ==============

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• [-] Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #229223 (closed)