fixing detecting deps dir for cover.spec files

Hey guys,

I've hit a *possible* a bug when trying to run ct tests with deps that have a cover.spec file. It seems that collect_glob/3 does not correctly determine that it should skip a cover.spec file inside a dependency directory and it ends up seeing all available cover.spec files (the one for the root project and the ones inside their deps).

This patch seems to work ok. 

Any thoughts about it?

Thanks in advance!