CRM 2016: Solution import: Cannot delete an active workflow definition.

When you upate an exisiting solution in CRM and receive an error equal to this one:

16:33:07.66
{793dab2e-c2a4-e611-8102-c4346bad41fc}
General SLA
Failure
0x8004500F
Cannot delete an active workflow definition.

This means there is an SLA record in the system which has the status "Active".
You first need to deactive that SLA record prior to importing the solution update.