Add grubby to handle latest grub2 changes

With latest grub2 installer, one should set the
kernel to be booted explicitly after update or
install of latest kernel

Signed-off-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>

testcases/InstallUpstreamKernel.py

@@ -128,8 +128,7 @@ def is_url(path):
             time.sleep(10)
             if not self.use_kexec:
                 # FIXME: Handle distributions which do not support grub
-                con.run_command(
-                    "grub2-mkconfig  --output=/boot/grub2/grub.cfg")
+                con.run_command("grubby --set-default /boot/vmlinuz-%s" % res[-1])
                 log.debug("Rebooting after kernel install...")
                 self.console_thread.console_terminate()
                 con.close()