PXB-3269: Jenkins fixes

1. Dumple tablespace key has two parts. Saving the keys during the
   backup and using them during prepare. We should use keys from dump
   file during prepare only
2. Free the memory allocated by fil_path_to_space_name() using a scope
   guard

storage/innobase/srv/srv0start.cc

@@ -397,8 +397,9 @@ static dberr_t srv_undo_tablespace_read_encryption(pfs_os_file_t fh,
                              : set_encryption(recv_key->ptr, recv_key->iv);
   } else if (is_enc) {
     // Condition 2: Page is encrypted
-    encryption_success = use_dumped_tablespace_keys ? load_key_from_dump()
-                                                    : load_key_from_page();
+    encryption_success = (use_dumped_tablespace_keys && !srv_backup_mode)
+                             ? load_key_from_dump()
+                             : load_key_from_page();
   } else {
     // Condition 3: If the page is not encrypted, we consider it successful
     encryption_success = true;

storage/innobase/xtrabackup/src/ddl_tracker.cc

@@ -391,7 +391,12 @@ static void copy_for_reduced(copy_thread_ctxt_t *ctxt) {
 static std::string convert_file_name(const space_id_t space_id,
                                      const std::string &file_path,
                                      const std::string &ext) {
-  std::string file_name = fil_path_to_space_name(file_path.c_str());
+  char *space_name = fil_path_to_space_name(file_path.c_str());
+  auto free_guard = create_scope_guard([&]() {
+    if (space_name != nullptr) ut::free(space_name);
+  });
+
+  std::string file_name(space_name);
   auto sep_pos = file_name.find_last_of(Fil_path::SEPARATOR);
   return file_name.substr(0, sep_pos + 1) + std::to_string(space_id) + ext;
 }