BUG/MEDIUM: jwe: Fix jwt.decrypt_alg_list to work correctly

BUG/MEDIUM: jwe: Fix jwt.decrypt_alg_list to work correctly

Function jwe_parse_global_alg_enc_list() handles both
jwt.decrypt_alg_list and jwd.decrypt_enc_list, but to know which array
to use, between the algorithms and encoding arrays to use, it was
checking the string to see if it matched jwe.supported_algorithms, so it
was always considering we were dealing with encodings, and
jwt.decrypt_alg_list could not possibly work.
Fix that by checking the right string.