added dropsonde-agent submodule

Signed-off-by: Johannes Petzold <jpetzold@pivotallabs.com>
[#67664790] Add helper scripts for local testing.

- Bump dropsonde-agent submodule
- Add dropsonde-agent tests to bin/test
- Add run-agent run-hurricanehunter send-hurricanehunter-request
  scripts for local testing.

Signed-off-by: Johannes Petzold <jpetzold@pivotallabs.com>
Bump dropsonde-agent submodule

Signed-off-by: Johannes Petzold <jpetzold@pivotallabs.com>