tests: reduce noise on MacOS

This should get rid of

    Openat: O_NOFOLLOW missing: flags = 0x0
    Fchmodat: adding missing AT_SYMLINK_NOFOLLOW flag
    sys_common_test.go:203: chmod on symlink should have failed, but did not. New mode=0333
    UnmountErr: "[...]/057376762.mnt" was not found in MountInfo, cannot check for FD leak

and add some context to

    --- FAIL: TestUtimesNano (0.00s)
    matrix_test.go:628: no such file or directory

See https://github.com/rfjakob/gocryptfs/pull/343#issuecomment-453888006
for full test output

0 files changed, 0 insertions, 0 deletions