Fix warnings, initialize a few variables, drop unused ones

  [ Arfrever Frehtes Taifersar Arahesis ]
  * key_mod/ecryptfs_key_mod_gpg.c,
    key_mod/ecryptfs_key_mod_pkcs11_helper.c,
    libecryptfs/key_management.c, utils/ecryptfs_unwrap_passphrase.c:
    Fix warnings, initialize a few variables, drop unused ones

Signed-off-by: Dustin Kirkland <kirkland@canonical.com>