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 <[email protected]>
Acked-by: Alistair Francis <[email protected]>
Reviewed-by: Markus Armbruster <[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>
Message-Id: <20171004030025[email protected]>
Reviewed-by: Daniel P. Berrange <[email protected]>
Signed-off-by: Eduardo Habkost <[email protected]>