Remove use of smart pointers.

Some versions of GCC apparently complain if C++ attributes are stripped
by use in templates (even if said attributes are completely useless
in the template context).  Other than going through heroics to suppress
the invalid warning, it seems the best approach is to revert to raw pointers.

src/XrdTpc/XrdTpcNSSSupport.cc

@@ -203,20 +203,21 @@ XrdTpcNSSSupport::Maintenance()
         return false;
     }
 
-    std::unique_ptr<DIR, decltype(&closedir)> dirp(fdopendir(fddir), &closedir);
+    DIR *dirp = fdopendir(fddir);
     if (!dirp) {
         m_log.Emsg("XrdTpc", "Failed to allocate a directory pointer");
         return false;
     }
 
     struct dirent *result;
-    while ((result = readdir(dirp.get()))) {
+    while ((result = readdir(dirp))) {
         //m_log.Emsg("Will parse file for CA certificates", result->d_name);
         if (result->d_type != DT_REG && result->d_type != DT_LNK) {continue;}
         if (result->d_name[0] == '.') {continue;}
         int fd = openat(fddir, result->d_name, O_RDONLY);
         if (fd < 0) {
             m_log.Emsg("XrdTpc", "Failed to open certificate file", result->d_name, strerror(errno));
+            closedir(dirp);
             return false;
         }
         file_smart_ptr fp(fdopen(fd, "r"), &fclose);
@@ -227,8 +228,10 @@ XrdTpcNSSSupport::Maintenance()
     }
     if (errno) {
         m_log.Emsg("XrdTpc", "Failure during readdir", strerror(errno));
+        closedir(dirp);
         return false;
     }
+    closedir(dirp);
 
     m_next_update.store(time(NULL) + 900, std::memory_order_relaxed);
     m_ca_file.reset(new_file.release());