Adjust the log event for Activate errors

[AnarManafov]

Make adjustment of the following log event:

Activate error: Unable to schedule collection <9391110637957382604> with path main/RecoGroup/RecoCollection)| |--- | --- | --- | --- | --- | --- | --- | --- | --- | ---|

If possible it should reflect why exactly the scheduling of the task/collection is not possible.

[rbx]

Just to listing one use case, to help identify cases where more info would help:

Activate error: Unable to schedule collection <250212107438957809> with path main/Sinks

In this case a collection in the topology had a groupname requirement for group x, while only y and z groups were submitted.

A hint in the log saying that "no group x exists" would help.

[rbx]

There is another use case for it: https://alice.its.cern.ch/jira/browse/EPN-272
Involves insufficient number of slots.