setenv: do console redirection even if previously unset

If "stdout" is not previously set, doing "setenv stdout lcd" had no
effect, since console redirection only worked if the environment
variable was already set; the second time you run setenv it worked.
Most default environments lack stdin/out/err definitions, so I'm sure
I'm not alone with this problem.

This patch simply moves a block of code out of a conditional, to do
the same work even if the variable was previously unset.

Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Andrea Gallo <andrea.gallo@stericsson.com>