libssh: when using IPv6 numerical address, add brackets

Reported-by: henrikjehgmti on github
Fixes curl#15522
Closes curl#15524

Author: bagder

lib/vssh/libssh.c

@@ -2191,7 +2191,14 @@ static CURLcode myssh_connect(struct Curl_easy *data, bool *done)
     return CURLE_FAILED_INIT;
   }
 
-  rc = ssh_options_set(ssh->ssh_session, SSH_OPTIONS_HOST, conn->host.name);
+  if(conn->bits.ipv6_ip) {
+    char ipv6[MAX_IPADR_LEN];
+    msnprintf(ipv6, sizeof(ipv6), "[%s]", conn->host.name);
+    rc = ssh_options_set(ssh->ssh_session, SSH_OPTIONS_HOST, ipv6);
+  }
+  else
+    rc = ssh_options_set(ssh->ssh_session, SSH_OPTIONS_HOST, conn->host.name);
+
   if(rc != SSH_OK) {
     failf(data, "Could not set remote host");
     return CURLE_FAILED_INIT;