Revert "Set leagcy grub as default for xen pv guest"

This reverts commit 62474fef7d492a698ebc49bea5169e732c9b4b11.

Conflicts:

	src/modules/BootCommon.ycp
Merge pull request #42 from WenhuaChang/master

Revert "Set leagcy grub as default for xen pv guest" (bnc#863820)