Mount btrfs fs with rescue= option

It looks like 'norecovery' is deprecated and has been removed in the v6.8-rc1
kernel. Replace it with 'rescue=nologreplay', which is a replacement
implemented since v5.9. The standalone 'nologreplay' option is also deprecated.

Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>

src/update_engine/postinstall_runner_action.cc

@@ -50,7 +50,7 @@ void PostinstallRunnerAction::PerformAction() {
                temp_rootfs_dir_.c_str(),
                "btrfs",
                mountflags,
-               "norecovery");
+               "rescue=nologreplay");
     if (errno == EEXIST) {
       /* When trying to mount an identical btrfs image twice because the old
        * and new partition are identical, the kernel refuses because same UUIDs