add securityContext to controller helm chart

[johnsonshih]

What this PR does / why we need it:
securityContext setting is missing in Controller helm chart. Add it to the chart to take the value for securityContext.

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

[johnsonshih]

/version patch