Stop software_deployments from passing empty keys

When software_deployments was given a body missing the "input_values"
field it would pass update info with input_values=None, which would
later fail and cause an internal server error.

This change prevents software_deployments from passing on NoneType
values.

Change-Id: I02e9c08bbd7429d808de1451de12cc02fc879ecb
Closes-Bug: 1319825