snort: add conflict with snort3

Both packages provides the same files:
- /usr/bin/u2boat
- /usr/bin/u2spewfoo
- /usr/bin/snort
- /etc/init.d/snort
- /etc/config/snort

So they should be in conflict.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

net/snort/Makefile

@@ -34,6 +34,7 @@ define Package/snort
   DEPENDS:=+libdaq +libdnet +libnghttp2 +libopenssl +libpcap +libpcre +libpthread +libtirpc +libuuid +zlib +luajit +SNORT_LZMA:liblzma
   TITLE:=Lightweight Network Intrusion Detection System
   URL:=http://www.snort.org/
+  CONFLICTS:=snort3
   MENU:=1
 endef