Unable to add a backup node in SolusVM 2: Server Error: Unable to connect to remote server.

Symptoms 

Unable to add a backup node in SolusVM 2:

SVM_ERROR: Server Error

Or
SVM_ERROR: The management server can't use this backup node: Couldn't check the backup node connectivity: Unable to connect to remote server.

Cause

SSH key for backup node was created incorrectly.

Resolution

1. Connect to SolusVM 2 Management node via SSH
2. Create SSH key pair using the following guide:
   How To Set Up SSH Keys