Fix a panic in connect-inject when the provided upstreams list is malformed

[dhiaayachi]

Changes proposed in this PR

• Fix a panic when parsing a malformed upstream, now a malformed upstream will be ignored
• Support multiple separators between upstreams (, , ).

How I've tested this PR

Added unit tests to test multiple scenarios including malformed upstream lists

How I expect reviewers to test this PR

N/A

Checklist

• [x] Tests added
• [x] CHANGELOG entry added

[dhiaayachi]

Thanks for fixing this :D! I think you're just missing a space separated case in your tests

This test case should cover it