use fuser instead of lsof to do health check

[Ian Kumlien]

The current health check uses a lot of cpu even on a unloaded system... There is faster ways that uses less cpu...

Reference:
https://github.com/openstack/kolla/blob/master/docker/base/healthcheck_socket

Current implementation:
#!/bin/bash
process=$1
socket=$2

# lsof truncate command name to 15 characters and this behaviour
# cannot be disabled
if [ ${#process} -gt 15 ] ; then
    process=${process:0:15}
fi
lsof -Fc -Ua $socket | grep -q "c$process"
---

timing:
time lsof -Fc -Ua /run/openvswitch/db.sock
real 0m1.571s

And quite a bit of cpu usage...

time fuser /run/openvswitch/db.sock
real 0m0.007s

Seems more reasonable....

How ever the output format is different.

/run/openvswitch/db.sock: 20

I assume something like:
pid=$(pidof $1)
socket=$2

fuser $socket |grep -q -E "^\s+$pid$" > /dev/null
---

Would work as a replacement, but it's only a quick hack...