Fix ComputerSystem.Reset error reporting

Report invalid ResetType values with
Base.1.19.ActionParameterValueNotInList instead of
Base.1.19.ActionParameterUnknown.

ResetType is a recognized action parameter, so an unsupported value
must be reported as an invalid enumeration value rather than an unknown
parameter name. This gives clients the correct error semantics and
actionable response details.

Tested:
The invalid-value response now identifies ResetType as a known
parameter and reports the supplied value as unsupported.

POST /redfish/v1/Systems/system/Actions/ComputerSystem.Reset with
{"ResetType":"Nope"} returns HTTP 400 and
Base.1.19.ActionParameterValueNotInList.

POST /redfish/v1/Systems/system/Actions/ComputerSystem.Reset with {}
continues to return HTTP 400 and Base.1.19.PropertyMissing.

Change-Id: Ieb71f89b0bedf5ceeaaa8c8c6d89c05ae4a4aac6
Signed-off-by: Joel Pullokaran Jesin <joelpj@ami.com>