Merge remote-tracking branch 'origin/tristan/haproxy-events' into v4.3.1
Bump to 4.3.1
Remove Content Length headers when using a proxy

As it seems that some proxy return a 400 when the CONNECT requests has
a content-length header.

(CONNECT requests shouldn’t have it)
Log that we are removing content length header
Merge branch 'fix_proxy'
Let the possibility to disable instance metadata collection

Fix #975
Merge with master