[BUG] metashield plugin should trust system pool if ca not specified

[thomasmitchell]

Describe the bug If CA certificate is not specified to the metashield plugin, then the SHIELD endpoint can never actually be trusted.

To Reproduce Steps to reproduce the behavior:

1. Make a metashield backup against a shield server with a system pool trusted certificate
2. Don't skip ssl validation
3. Don't specify a ca certificate
4. watch the backup fail

Expected behavior I expected the plugin to use the system certificate pool if no ca was given

Screenshots If applicable, add screenshots to help explain your problem.

SHIELD versions (please complete the following information):

• SHIELD Core: 8.7.2
• SHIELD CLI: n/a

Browser version(s) (please complete if reporting a web UI bug):

• OS: [e.g. OSX, windows]
• Browser: [e.g. firefox, chrome, safari]
• Version: [e.g. 22]

Additional context Add any other context about the problem here.

[sriniketh923]

Should be fixed now