Fix fil_ibd_open() on Windows.

In the merge of MDEV-11623 from 10.1 to 10.2, we added a call to
fsp_flags_try_adjust() which causes the data file to be opened
via the buffer pool while fil_ibd_open() is holding another open
handle to the file.

storage/innobase/fil/fil0fil.cc

@@ -4250,6 +4250,9 @@ fil_ibd_open(
 		}
 
 		if (purpose != FIL_TYPE_IMPORT && !srv_read_only_mode) {
+			df_remote.close();
+			df_dict.close();
+			df_default.close();
 			fsp_flags_try_adjust(id, flags & ~FSP_FLAGS_MEM_MASK);
 		}
 	}