testsuite: add test for kcmdline params with no value

Use "modprobe -c" to dump the configuration. Since we configure our
rootfs to have only a /proc/cmdline file, this should dump the knowledge
we have from its parsed content.

Test if <module>.option, without any value is correctly parsed, as fixed
in commit 493dc65 ("libkmod: Fix getting param with no value from kcmdline")
3 files changed