Support docker-in-docker by only returning the oldest dockerd process

[sophomeric]

Issue #, if available:

Description of changes:

Change the single pgrep occurance to pgrep -o, so that it can still match the main docker daemon process for those using docker-in-docker (dind). Else you end up with something like:

Trying to collect Docker daemon information... eks-log-collector.sh: line 503: [[: 4408
10332
13928: syntax error in expression (error token is "10332
13928")

	Warning: The Docker daemon is not running.

Because:

[ec2-user@ip-10-50-0-139 ~]$ pgrep dockerd
4408
10332
13928

[ec2-user@ip-10-50-0-139 ~]$ ps aufx | grep dockerd
root     10332  5.3  1.2 1148888 194396 ?      Sl   08:20   8:05  |       \_ dockerd
root     13928  1.6  0.5 950276 77848 ?        Sl   08:25   2:22          \_ dockerd
root      4408  2.5  0.5 2697464 92012 ?       Ssl  08:19   3:50 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

I considered using:

[ec2-user@ip-10-50-0-139 ~]$ pgrep -f /usr/bin/dockerd
4408

But as all docker-in-docker processes should be newer than the primary one, I preferred the -o should upstream ever change binary locations or in case someone is using their own custom built/compiled version in a different location.

[mogren]

Thanks @sophomeric