package/netopeer2: add patch to solve issue with empty group name

package/netopeer2: add patch to solve issue with empty group name

When building on a host that has no name specified for the used group in
/etc/group the script in install step will fail due to missing group name.

CMake Error at CMakeLists.txt:80 (message):
  Learning server module group failed: id: cannot find name for group ID 8000

The patch was taken from upstream and modified manually because of merge
conflicts.

Fixes:
http://autobuild.buildroot.net/results/f197ca1def9dc1292e1e784757f2da9d95484431/

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
Cc: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Cc: Matthew Weber <matthew.weber@rockwellcollins.com>
Reviewed-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>