vl: Eliminate defconfig variable

vl: Eliminate defconfig variable

Both -nodefconfig and -no-user-config options do the same thing
today, we only need one variable to keep track of them.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20171004030025.7866-2-ehabkost@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>