iscsi-target: TargetAddress in SendTargets should bracket ipv6 addresses

"The domainname can be specified as either a DNS host name, a
dotted-decimal IPv4 address, or a bracketed IPv6 address as specified
in [RFC2732]."

See https://bugzilla.redhat.com/show_bug.cgi?id=1206868Reported-by: Kyle Brantley <kyle@averageurl.com>
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/iscsi/iscsi_target.c

@@ -3468,6 +3468,7 @@ iscsit_build_sendtargets_response(struct iscsi_cmd *cmd,
 						tpg_np_list) {
 				struct iscsi_np *np = tpg_np->tpg_np;
 				bool inaddr_any = iscsit_check_inaddr_any(np);
+				char *fmt_str;
 
 				if (np->np_network_transport != network_transport)
 					continue;
@@ -3495,8 +3496,12 @@ iscsit_build_sendtargets_response(struct iscsi_cmd *cmd,
 					}
 				}
 
-				len = sprintf(buf, "TargetAddress="
-					"%s:%hu,%hu",
+				if (np->np_sockaddr.ss_family == AF_INET6)
+					fmt_str = "TargetAddress=[%s]:%hu,%hu";
+				else
+					fmt_str = "TargetAddress=%s:%hu,%hu";
+
+				len = sprintf(buf, fmt_str,
 					inaddr_any ? conn->local_ip : np->np_ip,
 					np->np_port,
 					tpg->tpgt);