**- Why I did it**
We were building a custom version of Supervisor because I had added patches to prevent hangs and crashes if the system clock ever rolled backward. Those changes were merged into the upstream Supervisor repo as of version 3.4.0 (http://supervisord.org/changes.html#id9), therefore, we should be able to simply install the vanilla package via pip. This will also allow us to easily move to Python 3, as Python 3 support was added in version 4.0.0.
**- How I did it**
- Remove Makefiles and patches for building supervisor package from source
- Install Python 3 supervisor package version 4.2.1 in Buster base container
- Also install Python 3 version of supervisord-dependent-startup in Buster base container
- Debian package installed binary in `/usr/bin/`, but pip package installs in `/usr/local/bin/`, so rather than update all absolute paths, I changed all references to simply call `supervisord` and let the system PATH find the executable to prevent future need for changes just in case we ever need to switch back to build a Debian package, then we won't need to modify these again.
- Install Python 2 supervisor package >= 3.4.0 in Stretch and Jessie base containers
hardware daemons are not supported in kvm vs platform now
admin@vlab-01:/usr/share/sonic/device/x86_64-kvm_x86_64-r0$ docker exec -it pmon bash
root@vlab-01:/# supervisorctl status
fancontrol STOPPED Not started
lm-sensors STOPPED Not started
rsyslogd RUNNING pid 23, uptime 0:03:09
start.sh EXITED Apr 22 09:07 AM
supervisor-proc-exit-listener RUNNING pid 17, uptime 0:03:10
Signed-off-by: Guohan Lu <lguohan@gmail.com>
