tests/cli: escape filenames in TestBadname logs

I just got this message (not reproducible) with unescaped
binary garbage.

  UnmountErr: "/var/tmp/gocryptfs-test-parent-1026/114471933/TestMountBackground.899727687.mnt" was not found in MountInfo, cannot check for FD leaks
  UnmountErr: "/var/tmp/gocryptfs-test-parent-1026/114471933/TestConfigPipe.212912444.mnt" was not found in MountInfo, cannot check for FD leaks
  DecryptName "mzaZRF9_0IU-_5vv2wPC_i": unPad16 error: Padding too long, padLen=49 > 16
  OpenDir ".": invalid entry "KqQ346cuOAFHv_qSta5PhAwrongPattern": bad message
  DecryptName "mzaZRF9_0IU-_5vv2wP_in": unPad16 error: Padding byte at i=10 is invalid
  --- FAIL: TestBadname (0.11s)
      cli_test.go:885: Case 5 failed: 'KqQ346cuOAFHv_qSta5P_invalid_file GOCRYPTFS_BAD_NAME' in [file_invalid_file GOCRYPTFS_BAD_NAME,file,mzaZRF9_0IU-_5vv2wPC_invalid_file GOCRYPTFS_BAD_NAME,file GOCRYPTFS_BAD_NAME,�*A���y���Gfnvalid_file GOCRYPTFS_BAD_NAME,mzaZRF9_0IU-_5vv2wP_invalid_file GOCRYPTFS_BAD_NAME]
  Invalid cipherdir: directory /var/tmp/gocryptfs-test-parent-1026/114471933/TestInitNotEmpty not empty
  FAIL
  FAIL	github.com/rfjakob/gocryptfs/tests/cli	4.817s

0 files changed, 0 insertions, 0 deletions