Remove unnecessary etcd systemd Alias directive

[carlpett]

What this PR does / why we need it:
This PR removes the Alias directive from the systemd unit file for etcd. Since the specified alias is the same as the name of the unit itself, systemd enable etcd fails.

Which issue this PR fixes
fixes #2282 (although it is already marked as fixed...)

Special notes for your reviewer:
No

Release note:

Fix etcd systemd unit

[jackfrancis]

Hi @carlpett, thanks. To properly triage this as a bug: I just built a cluster off of HEAD, and got this:

$ systemctl is-enabled etcd.service
enabled

[carlpett]

Sorry @jackfrancis, I didn't understand - was this a question to me?

On our clusters built with 0.13, systemctl status etcd showed something similar to Loaded: loaded (/etc/systemd/system/etcd.service; disabled; vendor preset: disabled) (I don't have the output available any more, and we fixed locally it on all masters). We didn't use is-enabled, but it should have reported disabled in this case.

As a more detailed description of the error, systemctl enable etcd gives Failed to enable unit: Invalid Argument (wonderfully clear...) if the alias is there. The reason being it tries to create two symlinks with the same name, etcd (from the unit name) and etcd (from the alias).

[jackfrancis]

I was wondering if etcd.service was not being enabled at present, so I built a cluster to verify. (I was able to verify that master/HEAD is not broken.)

Unfortunately v0.13.0 is the affected version with this bug. It sounds like (1) you have an action to manually fix this on your clusters and (2) if the alias duplication which this PR removes hadn't been there #1 would have been easier for you.

Does that sound right?

I'll run this through E2E and approve/merge accordingly.

Thanks!

[jackfrancis]

lgtm

[carlpett]

Ah, right.
We manually fixed our clusters this morning, so that's taken care of :)

[carlpett]

Thanks!