When a new globalvar with a value is created and the corresponding
nvvar exists, then the globalvar gets the value of the nvvar, not
from the newly assigned value as expected.

nv quux=foo; global quux=bar; echo ${global.quux}

Should give "bar", not "foo". Fix this.

Reported-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>