Revert "vnstat: update to v1.16"

This reverts commit 79b6e9dc61.

Undo the recent vnstat update due to upstream bugs preventing database
restoration.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

net/vnstat/patches/003-no_install_uname.patch

@@ -0,0 +1,15 @@
+--- a/Makefile
++++ b/Makefile
+@@ -33,12 +33,6 @@ debug:
+ install:
+ 	@echo "Installing vnStat..."
+ 
+-# check that system is really Linux
+-	@if [ `uname` != "Linux" ]; \
+-	then echo "This isn't a Linux system. Maybe 'make bsdinstall' is what you need?"; \
+-	false; \
+-	fi
+-
+ # check that there's something to install
+ 	@if [ ! -f "src/vnstat" ] || [ ! -f "src/vnstatd" ]; \
+ 	then echo "Nothing to install, run make first."; \