Fix wrong Host header detection

[Slach]

after update my funkload test is broken with errror

File "/usr/local/lib/python2.7/dist-packages/funkload/PatchWebunit.py", line 391, in WF_fetch
if not webproxy and not 'Host' in self.extra_headers.keys():
AttributeError: 'list' object has no attribute 'keys'

[Slach]

ok. i try fix it

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