MINOR: tools: split is_addr() and is_inet_addr()

The is_addr() function indicates if an address is set and is an IPv4
or IPv6 address. Let's rename it is_inet_addr() and make is_addr()
also accept AF_UNIX addresses.
diff --git a/include/common/standard.h b/include/common/standard.h
index 86cafb5..8acd277 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -627,7 +627,7 @@
 /* returns non-zero if addr has a valid and non-null IPv4 or IPv6 address,
  * otherwise zero.
  */
-static inline int is_addr(struct sockaddr_storage *addr)
+static inline int is_inet_addr(const struct sockaddr_storage *addr)
 {
 	int i;
 
@@ -642,6 +642,17 @@
 	return 0;
 }
 
+/* returns non-zero if addr has a valid and non-null IPv4 or IPv6 address,
+ * or is a unix address, otherwise returns zero.
+ */
+static inline int is_addr(const struct sockaddr_storage *addr)
+{
+	if (addr->ss_family == AF_UNIX)
+		return 1;
+	else
+		return is_inet_addr(addr);
+}
+
 /* returns port in network byte order */
 static inline int get_net_port(struct sockaddr_storage *addr)
 {