Move After to proper systemd unit file section.

[pdrakeweb]

Move the After= configuration statement from the [Service] section to the [Unit] section where it belongs.

The current code results in syslog messages like this:

11/05/2021
5:35:48.546 AM +0000
service.systemd v2 i-###########.us-east-1a ##.##.##.## undef 4 [/etc/systemd/system/codedeploy-agent.service:6] Unknown lvalue 'After' in section 'Service'

See syslog documentation for supporting evidence:
https://www.freedesktop.org/software/systemd/man/systemd.unit.html
https://www.freedesktop.org/software/systemd/man/systemd.service.html

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[coveralls]

Coverage remained the same at 47.849% when pulling c3f315d on pdrakeweb:service-after into 3c39d54 on aws:master.