Log Message:
Update exabgp to version 3.4.11.

Pkgsrc changes: adapt PLIST; the healtcheck script moved

Upstream changes:

This release is a bug fix "mostly" release, back porting fixes
performed in master.

 * Change: install healthcheck in bin
 * Feature: Allow single line flow route requested by: Pavel Odintsov
 * Feature: show route (extensive) can take a neighbor as parameter
   requested by: jtkdpu
 * Fix: Do shutdown when waiting for a new connection to a peer
 * Fix: Bad ASN enconding when ASN4 is not negotiated reported by:
   Orangefish on github
 * Fix: Shutdown when waiting for a new outgoing connection to establish
 * Fix: JSON counter reported by:
 * Fix: JSON flow printing for source and destination
 * Fix: Do not always locate exabgp.env reported by: Florian Obser
 * Fix: Correctly drop root privileges reported by: Florian Obser
 * Fix: validation of flow routes
 * Fix: Python differences between Unix version breaking process forking
 * Fix: Allow = with flowspec singleton reported by: Pavel Odintsov
 * Fix: selfcheck feature
 * Fix: do not refuse to parse multiple MP attributes in an update
 * Fix: possible bug with attribute information due to caching