[HDDS-1060] Add API to get OM certificate from SCM CA

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.4.0
• Labels: Blocker Security
• Sprint: HDDS BadLands
• Assignee: Ajay Kumar
• Reporter: Ajay Kumar
• Created: 06/Feb/19 20:39
• Updated: 20/Feb/19 19:50
• Resolved: 20/Feb/19 19:36

Description

Datanodes/OM need OM certificate to validate block tokens and delegation tokens.
Add API for:
1. getCertificate(String certSerialId): To get certificate from SCM based on certificate serial id.
2. getCACertificate(): To get CA certificate.