qemu: Fix broken autostart symlink after renaming domain

qemu: Fix broken autostart symlink after renaming domain

If a domain is configured to start on boot, it has a symlink to the
domain definition inside the autostart directory. If you rename this
domain, the definition is renamed too. The symlink need to be pointed to
this renamed file. This commit recreates the symlink after renaming the
XML file.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1594985

Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
Signed-off-by: Erik Skultety <eskultet@redhat.com>