net-mgmt/netdata: Update to 1.8.0
Update includes:

bug fix: streaming slaves consuming 100% CPU
Happened Under certain conditions, especially under FreeBSD and macOS slaves.

bug fix: missing alarm notifications on netdata masters
Because of messing cached alarm state, sometimes the notifications were not

always sent, although being visible at the dashboards.

bug fix: streamed charts with duplicate names
There was a minor issue with charts that were created with name aliases.

new plugin:
python.d.plugin now supports HTTP keep-alive via using urllib3.
This enables HTTP keep-alive on all connections, which allows netdata to have

permanent connections to third party web applications.

Reviewed by: mat (mentor)
Approved by: mat (mentor)
Sponsored by: Netzkommune GmbH
Differential Revision: https://reviews.freebsd.org/D12408