wireprotov1server: use binascii.unhexlify...
wireprotov1server: use binascii.unhexlify
The "hex" codec doesn't exist in Python 3. We could use
`codecs.decode(h, 'hex_codec')`. But `binascii.unhexlify()`
exists and should work the same on Python 2 and 3.
Differential Revision:
https://phab.mercurial-scm.org/D5755
