CMFActivity,syncml: stop using a dedicated log file
$INSTANCE_HOME/log only exists in runUnitTest instances, this code had no effect in slapos instances.
It is a future problem because it depends on the Signals module (part of ZServer package) and we are removing this dependency in the python 3 port.
For the SynchronizationTool, it was even more problematic because it can cause the component not to loed, with an error like:
ImportError: erp5.component.tool.SynchronizationTool: cannot load Component SynchronizationTool (signal only works in main thread)