gtools: Support Ganeti 2.10 too

Since Ganeti 2.10, the private ganeti module is installed and linked
under /etc/ganeti/share. If this path is found, include this path
in eventd.py before importing any ganeti related modules. Otherwise
import ganeti from /usr/share/ganeti.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>