<bugfix>runtestsuite.py should not care about empty string arguments</bugfix>
<bugfix>runtestsuite.py should not care about empty string arguments</bugfix>

BuildBot on OSX generates empty string arguments as a side-effect, and these were interpreted as modules to test.

runtestsuite.py: Remove empty string arguments

celiafish/VisTrails,VisTrails/VisTrails,minesense/VisTrails,celiafish/VisTrails,Nikea/VisTrails,minesense/VisTrails,celiafish/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails,minesense/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,hjanime/VisTrails,Nikea/VisTrails,hjanime/VisTrails,celiafish/VisTrails,minesense/VisTrails,hjanime/VisTrails