Annoyingly, for JSON formatting protojson randomly selects a spacing
method (one space or two spaces) depending on a hash of some sections of
the Go binary, to discourage depending on its output being stable.  This
breaks some checks in the CLI tests of the contents of fscrypt.conf and
the output of 'fscrypt status'.  As there doesn't appear to be a
straightforward alternative currently, for now just update the tests to
take into consideration the possible extra space.

The test user's user keyring is still linked into root's user keyring at
the end of the test.  This is making the test flaky, as there is a
failure that only occurs the first time it is run.  Fix the test to
restore the initial state.  This makes it consistently fail (to be fixed
by the next commit).

'fscrypt lock' on a v1-encrypted directory doesn't warn about in-use
files, as the kernel doesn't provide a way to easily detect it.

Instead, implement a heuristic where we check whether a subdirectory can
be created.  If yes, then the directory must not be fully locked.

Make both 'fscrypt lock' and 'fscrypt status' use this heuristic.

Resolves https://github.com/google/fscrypt/issues/215

Test using v1 encryption policies (deprecated).