lib, bgpd, tests: Refactor FILTER_X in zebra.h

lib/zebra.h has FILTER_X #define's.  These do not belong there.
Put them in lib/filter.h where they belong.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/tests/bgp_mpath_test.c b/tests/bgp_mpath_test.c
index dbbf0dd..a953ce9 100644
--- a/tests/bgp_mpath_test.c
+++ b/tests/bgp_mpath_test.c
@@ -29,6 +29,7 @@
 #include "linklist.h"
 #include "memory.h"
 #include "zclient.h"
+#include "filter.h"
 
 #include "bgpd/bgpd.h"
 #include "bgpd/bgp_table.h"