Fix EC2 example and set WorkingDirectory for systemd service

[crhino]

With Consul 1.14.0+, we set the new tls.defaults settings in Consul configuration. Because the client config uses relative paths when downloaded from HCP, the consul service was unable to start up. This PR also fixes invalid local references in the examples terraform.

Jan 10 14:29:44 ip-10-0-1-226 consul[84162]: ==> Error loading from ./ca.pem: open ./ca.pem: no such file or directory
Jan 10 14:29:44 ip-10-0-1-226 systemd[1]: consul.service: Main process exited, code=exited, status=1/FAILURE
Jan 10 14:29:44 ip-10-0-1-226 systemd[1]: consul.service: Failed with result 'exit-code'.
Jan 10 14:29:44 ip-10-0-1-226 systemd[1]: consul.service: Scheduled restart job, restart counter is at 5.

By setting WorkingDirectory in the systemd service file (ref), we can use relative paths from the client config without modifying them.

Screenshots after modifying the service file:

[riddhi89]

Great find!