tools/insmod: use single control variable

tools/insmod: use single control variable

Currently we're returning success, if any of the pre libkmod checks
fail. That's because err is our local variable, while r is the (exit)
resutlt. In practise we don't need the distinction, so just drop the
former.

Reported by clang.

Fixes: ca8f04e8 ("tools/insmod: add syslog and verbose options")
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/180
[ add blank lines, remove extra braces ]
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>