Fix permissions on 99network-settings

- If 99network-settings isn't world readable, pbuilder fails to copy it
in. The permissions of the file are determined by your umask at checkout
time, so just set them after the copy to avoid issue.

Change-Id: Ib230f904864c0dcaf3194535de642fcf9f43d040
diff --git a/docker.mk b/docker.mk
index 3143a6a..f269f08 100644
--- a/docker.mk
+++ b/docker.mk
@@ -83,7 +83,8 @@
 			passwd -d $(shell id -u -n); \
 			echo "$(shell id -u -n) ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers; \
 			adduser $(shell id -u -n) docker; \
-			sudo cp /rootdir/build/99network-settings /etc/apt/apt.conf.d/;\
+			sudo cp /rootdir/build/99network-settings /etc/apt/apt.conf.d/; \
+			sudo chmod 644 /etc/apt/apt.conf.d/99network-settings; \
 			/etc/init.d/docker start; \
 			sudo -E -u $(shell id -u -n) /bin/bash -c "source build/setup.sh; m \
 			-j$$(nproc) $*";'