PSHB: work-around for SuperFeeder
PSHB: work-around for SuperFeeder

Feeds using SuperFeeder for PubSubHubbub push had timeout problems
during substription.
SuperFeeder bot was returning 422 "We could not verify your callback
Error: ETIMEDOUT"
It seems to be due to the the fact that SuperFeeder bot uses keep-alive
but expects the server to close the connection.
https://github.com/FreshRSS/FreshRSS/issues/312#issuecomment-73716936

Alkarex/FreshRSS,aledeg/FreshRSS,Alkarex/FreshRSS,FreshRSS/FreshRSS,marienfressinaud/FreshRSS,Alkarex/FreshRSS,Alkarex/FreshRSS,marienfressinaud/FreshRSS,FreshRSS/FreshRSS,romibi/FreshRSS,aledeg/FreshRSS,aledeg/FreshRSS,romibi/FreshRSS,aledeg/FreshRSS,FreshRSS/FreshRSS,romibi/FreshRSS,marienfressinaud/FreshRSS,romibi/FreshRSS,FreshRSS/FreshRSS,marienfressinaud/FreshRSS