meta-hipos: rename watchdog to hipos-watchdog

The systemd service implementing our watchdog via drbcc conflicts
with another recipe called watchdog. Rename to hipos-watchdog to
solve this conflict.

Signed-off-by: Angelika Tobisch <tobisch@dresearch-fe.de>
meta-hipos: change install directories

The link used by systemd that marks hipos-watchdog as wanted
by multi-user.target will now be created in /etc/systemd/system
instead of /lib/systemd/system.

This is consistent with systemd's behavior when using
enable/disable and ensure that this works as expected.

Signed-off-by: Angelika Tobisch <tobisch@dresearch-fe.de>