Cleanup set_connect_fail debug log (#13091)

* Cleanup set_connect_fail debug log

* Fix args

* Include swoc header explicitly

Author: masaori335

include/proxy/http/HttpTransact.h

@@ -47,6 +47,8 @@
 #include "proxy/ProxySession.h"
 #include "tscore/MgmtDefs.h"
 
+#include "swoc/bwf_ex.h"
+
 #include <cstdint>
 #include <cstdio>
 #include <string>
@@ -953,7 +955,13 @@ class HttpTransact
       if (e != EIO) {
         this->cause_of_death_errno = e;
       }
-      Dbg(_dbg_ctl, "Setting upstream connection failure %d to %d", original_connect_result, this->current.server->connect_result);
+
+      if (_dbg_ctl.on()) {
+        std::string buf;
+        swoc::bwprint(buf, "Setting connect_result {::s} to {::s}", swoc::bwf::Errno(original_connect_result),
+                      swoc::bwf::Errno(this->current.server->connect_result));
+        Dbg(_dbg_ctl, "%s", buf.c_str());
+      }
     }
 
     MgmtInt