[BUG] Implement mutex lock to handle concurrent ssh sessions

[bhrg3se]

Describe the bug:

SSH session details are kept in map which are not safe for concurrent use. So we need to implement a mutex lock or use sync.Map. So when ssh usage is high, server might panic and crash.

Log file / Code snippet / Screenshots:

Scope of issue:

• [ ] TRASA codebase
• [ ] dashboard
• [x] server
• [ ] mobile app
• [ ] browser extension
• [ ] device agent
• [ ] website/docs