Use executeAsSubAlg() in more places to run child algoritms.

[mantid-builder]

Original Reporter: @jzikovsky

Original Owner: @jzikovsky

Refs http://trac.mantidproject.org/mantid/ticket/2319. There are about 20 spots where it could use it:

Mantid
Framework
Algorithms
src
CalculateEfficiency.cpp
66: childAlg->execute(); 
CalculateTransmission.cpp (2 matches)
189: childAlg->execute(); 
224: childAlg->execute(); 
ConvertUnits.cpp
656: childAlg->execute(); 
DetectorDiagnostic.cpp (2 matches)
72: childAlg->execute(); 
204: childAlg->execute(); 
DiffractionFocussing.cpp (3 matches)
98: childAlg->execute(); 
177: childAlg->execute(); 
214: childAlg->execute(); 
FindDeadDetectors.cpp
148: childAlg->execute(); 
FlatBackground.cpp
313: childAlg->execute(); 
GetEi.cpp
261: childAlg->execute(); 
GetEi2.cpp (2 matches)
239: childAlg->execute(); 
499: childAlg->execute(); 
HRPDSlabCanAbsorption.cpp
176: childAlg->execute(); 
MedianDetectorTest.cpp
175: childAlg->execute(); 
NormaliseToMonitor.cpp
225: childAlg->execute(); 
RemoveBins.cpp
211: childAlg->execute(); 
SumRowColumn.cpp
112: childAlg->execute(); 
Unwrap.cpp
400: childAlg->execute(); 

[mantid-builder]

This issue was originally trac ticket 2426