btrfs: remove btrfs_handle_fs_error() after failure to recover log trees

There is no need to call btrfs_handle_fs_error() (which we are trying to
deprecate) if we fail to recover log trees:

1) Such a failure results in failing the mount immediately;

2) If the recovery started a transaction before failing, it has already
aborted the transaction down in the call chain.

So remove the btrfs_handle_fs_error() call, replace it with an error
message and assert that the FS is in error state (so that no partial
updates are committed due to a transaction that was not aborted).

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>