confd: add ip proto when setting static ip

There might be more places in confd where this is needed. This works
for the most basic use case.

The proto set here is picked up by statd and converted into a YANG
origin, which is exposed to the user.

Signed-off-by: Richard Alpe <richard@bit42.se>

src/confd/src/ietf-interfaces.c

@@ -381,7 +381,7 @@ static int netdag_gen_diff_addr(FILE *ip, const char *ifname,
 	    is_std_lo_addr(ifname, adrd.new, pfxd.new))
 		addcmd = "replace";
 
-	fprintf(ip, "address %s %s/%s dev %s\n", addcmd,
+	fprintf(ip, "address %s %s/%s dev %s proto 4\n", addcmd,
 		adrd.new, pfxd.new, ifname);
 	return 0;
 }