cmd-exec payload should be payload, not err msg.

cmd-exec payload should be payload, not err msg.

Issue-ID: CCSDK-2549

fixes:
1. CMD-exec returns payload as JSON object.
There was some regression where we overwrite returned JSON with errMsg.
2. adds 100ms delta to executionTimeout, as was in our downstream version
(want to guarantee that we get grpc timeout exception on BP side
rather than coroutine w/o waiting extra)
3. setNodeOutputErrors should not have ability to set execution status
to success.

rev1. initial import
rev2. reworked the calls to setNodeOutputErrors: addError was brought out of it
as we can set the node execution error based on prepare.env or execution.
rev3. did not mean to add BlueprintRuntimeService change

Signed-off-by: Oleg Mitsura <oleg.mitsura@amdocs.com>
Change-Id: I6d509df5ae51598f33ab9f0ea53806d653cf79c0
(cherry picked from commit c48e0797fd577ec10b7c8978c19b02f6a84a3950)