Fix for MRP 370

MRP 370 'Test runtests doesn't report result after end'
Created special executor with empty log processing and
test for it.
Improved exit code processing in SingleProcessBase.
Added syncexitcode member to SshProcess for separating
exit code from sync and async executions. Replaced
'exitcode' to 'syncexitcode' in some libraries.

Change-Id: I0791e3ffad8c697d378d97eaed5a53d297e6f890
Merge "Fix for MRP 370"