grabber.py: disable pycurl SSL validation
grabber.py: disable pycurl SSL validation

While this might seem like a bad idea, the SSL validation step is rather
pointless in oe-lite as we verify what we are downloading using source
signatures anyway. By disabling this we avoid a lot of problems with
broken certificate handling (Ubuntu 14.04 I am looking at you!)

Both current debian stable and ubuntu 14.04 LTS ships with a pycurl
package built agains GnuTLS. GnuTLS on these distro versions is very
old and is not searching for the installed root certificates resulting
in:

urlgrabber.grabber.URLGrabError: [Errno 14] curl#60 -
"Local CA certificate failed"

oe-lite/urlgrabber,oe-lite/urlgrabber,oe-lite/urlgrabber,oe-lite/urlgrabber