Don't use the first token uname -n as the hostname

[yujuhong]

This change partially reverts the change made in #7910, which takes only the
first token of uname -n as the hostname.

[vmarmol]

LGTM, thanks for the quick fix @yujuhong!

[yujuhong]

/cc @timothysc, this should fix the breakage in your cluster. FYI, in #6499, we discussed whether it's sensible to use only the first token of the FQDN as a unique hostname, and most people were okay with it. Is it not true in your case?

[timothysc]

It should default the node checkin to fqdn, we have our setup explicitly set to check as there are many theifdoms , e.g. bob.redhat.com, bob.test.redhat.com, bob.prod.redhat.com

/cc @rrati @eparis @jayunit100

[dchen1107]

@yujuhong What is the problem we are fixing here?

#7072 along with other prs from different cloud provider owners removed fqdn dependencies from a node name.

[vmarmol]

@dchen1107 @timothysc was running into issues with our latest change. We changed all uses of the hostname to be the first section, this may not be unique in all settings.

[yujuhong]

@dchen1107, if I understand correctly, @timothysc's cluster uses FQDNs (probably through uname -n?) as the hostnames of the node. The first sections of the these FQDNs are not unique, leading conflicts after #7910 was merged.

[timothysc]

@yujuhong correct.

[timothysc]

LGTM, are we waiting on something?

[vmarmol]

Merging to fix breakage, we can discuss more here or in an issue :)