update to latest HEAD
- Read FS yumvars before yum.conf setup, and reread if installroot changed.
- Call systemd Inhibit, to inhibit shutdowns during transactions. BZ 1109930.
- Have check provides check directly against the rpm index, and then quit.
- Read env vars in readStartupConfig() to make them work in yum.conf. BZ 1102575
- Add rules for naming files in /etc/yum/vars to yum.conf man page.