Privileges: PROTECTION_SOURCE_MODIFY

If the request is successful, the Cohesity agents on the specified
Physical Servers are upgraded to the agent release
currently available from this Cohesity Cluster.
For example if the Cluster is upgraded from 3.7.1 to 4.0,
the agents on the specified Physical Servers can be upgraded to 4.0 using
this POST operation.
To get the agentIds to pass into this operation, call
GET /public/protectionSources with the environment set to 'KPhysical'.
In addition this GET operation returns the agentUpgradability field, that
indicates if an agent can be upgraded. Use the agentUpgradability field
to determine which Physical Servers to upgrade using this
POST /public/physicalAgents/upgrade operation.

WARNING: Only agents at a particular Cohesity release can be
upgraded using this operation.
See the Cohesity online help for details.

Returns the status of the upgrade initiation.