tools: firmware: check for distro fallback udev cancel rule

commit afb999cdef69148f366839e74470d8f5375ba5f1 upstream.

Some distributions (Debian, OpenSUSE) have a udev rule in place to cancel
all fallback mechanism uevents immediately. This would obviously
make it hard to test against the fallback mechanism test interface,
so we need to check for this.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>