Bug#741365: Unnecessary device-mapper errors - /usr/share/grub/grub-mkconfig_lib

[Steve Graham]

I also have a system with no LVM requirement.

The lines "/proc/devices: No entry for device-mapper found" are emitted by grub-probe. In general, 
the grub scripts redirect grub-probe's stderr to /dev/null to suppress these, but the subroutines in 
/usr/share/grub/grub-mkconfig_lib aren't completely consistent in doing so.

I quickly hacked /usr/share/grub/grub-mkconfig_lib to add the redirection on every invocation of 
grub-probe and the messages have gone away.

For example, the original line
    partmap="`"${grub_probe}" --device $@ --target=partmap`"
was changed to
    partmap="`"${grub_probe}" --device $@ --target=partmap`" 2> /dev/null

(I'm not supplying an actual diff because I haven't checked the full logic and may have broken 
something. It was just a quick experiment.)