Deduplicated ValidateGroupCount and fixed incorrect usage

[DrizztDoUrden]

convolutionocl.cpp version of ValidateGroupCount has been updated without changes to a copy in problem.cpp which made them incomaptible. PR moves the code to problem.cpp, changes all the call sites and removes the copy in convolutioncol.cpp

Also fixed incorrect usage of Problem::ValidateGroupCount in find 2.0 for the transposed cases