cilium: only start daemon's monitoring agent after base datapath setup
cilium: only start daemon's monitoring agent after base datapath setup

The latter is supposed to set up cilium_events, only then we can
fetch the pinned map from BPF fs.

The NewAgent() basically sets up the unix domain socket file under
unix:///var/run/cilium/monitor1_2.sock, and once connection got
accepted, it's reading out BPF perf event buffer (logs "Beginning
to read perf buffer" to the agent). Then it tries to fetch cilium_events
map from BPF fs, but if this happens at a time before init.sh was
run, agent will bail out with an error:

  level=fatal msg="Cannot initialise BPF perf ring buffer sockets" error="Unable to get object /sys/fs/bpf/tc/globals/cilium_events: no such file or directory" startTime="2019-07-24 18:13:00.920286144 +0000 UTC m=+1.662936719" subsys=monitor-agent

Move this to after d.init() such that it is able to open cilium_events.

Fixes: #8671
Signed-off-by: Daniel Borkmann <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@iogearbox.net>

michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium-team/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,cilium-team/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium