Return discovered devices that fails to get ip/mac address if ip/mac filters are not used

[johnsonshih]

…address filters are not used

What this PR does / why we need it:
ref #250
ref #635

Currently, Onvif DH will not return discovered devices if it fails to get devices' ip/mac address. This is not necessary if ip/mac address filter is not used. This PR change Onvif DH so when ip/mac address filter is not used, Onvif DH returns discovered devices no matter it gets ip/mac address from that device (other filters still applied).

When returning discovered devices, Onvif DH does best efforts to retrieve ip/mac address and set to environment variables. If ip/mac address filter is not used, it is possible that ip/mac address environments won't be set (if Onvif DH cannot retrieve ip/mac address from devices).

Special notes for your reviewer:

If applicable:

• this PR has an associated PR with documentation in akri-docs
• this PR contains unit tests
• added code adheres to standard Rust formatting (cargo fmt)
• code builds properly (cargo build)
• code is free of common mistakes (cargo clippy)
• all Akri tests succeed (cargo test)
• inline documentation builds (cargo doc)
• all commits pass the DCO bot check by being signed off -- see the failing DCO check for instructions on how to retroactively sign commits

[diconico07]

Except the refactor I mentioned and the need for some unit test, this is good.

[johnsonshih]

/version patch