HDDS-14099. CI tools are reinstalled if not on path

[adoroszlai]

What changes were proposed in this pull request?

Dev tools (like Hugo) are reinstalled on every run if they are not also available on $PATH. This is caused by the sanity check (which) before adding the tool to $PATH.

https://issues.apache.org/jira/browse/HDDS-14099

How was this patch tested?

Initial run:

$ rm -fr .dev-tools && ./hadoop-ozone/dev-support/checks/docs.sh
...
Installed hugo in .dev-tools/hugo
...
Start building sites … 
...

Re-run, not installed again:

$ ./hadoop-ozone/dev-support/checks/docs.sh
...
Start building sites … 
...

Dir exists, but tool does not work, installed:

$ rm .dev-tools/hugo/bin/hugo && ./hadoop-ozone/dev-support/checks/docs.sh
...
Installed hugo in .dev-tools/hugo
...
Start building sites … 
...

CI:
https://github.com/adoroszlai/ozone/actions/runs/19993620689