This ensures systemctl start matrix-synapse returns only after synapse
is actually started, which is very useful for automated deployments.

Fixes #5761

Signed-off-by: Dexter Chua <dec41@srcf.net>

* implement `reload` by sending the HUP signal

According to the 0.99 release info* synapse now uses the HUP signal to reload certificates:

> Synapse will now reload TLS certificates from disk upon SIGHUP. (#4495, #4524)

So the matrix-synapse.service unit file should include a reload directive.

Signed-off-by: Дамјан Георгиевски <gdamjan@gmail.com>