Adjust status message for v1 policies unlocked by another user and fix cli-tests/t_v1_policy

When 'fscrypt status DIR' detects that a v1-encrypted directory is still
usable but its key seems to be absent, it shows the status as
"Unlocked: Partially (incompletely locked)".  But actually it can also
be the case that the directory is unlocked by another user.  Adjust the
status message accordingly.

This commit also fixes cli-tests/t_v1_policy.

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).

* cmd/fscrypt: fix 32-bit build
* travis.yml: build 32-bit binary

statfs.Bsize actually has platform-dependent type, despite the Go
documentation listing it as int64.  Fix the build for 32-bit platforms
by casting it to int64.

Resolves https://github.com/google/fscrypt/issues/233

Don't let people check in code that breaks 32-bit builds.

Update https://github.com/google/fscrypt/issues/233

Use %q, in case the paths contain whitespace.  Also clean the directory
path to remove trailing slashes before appending the ".new" suffix.

Update https://github.com/google/fscrypt/issues/220