add step to enable pmm2-client repo before install clients

[brenobaima]

No description provided.

[zelmario]

Tested this on a Rocky 9 (os:el9) node with pmm-client:2.44.1-6, running from the source tree (local roles/ mounted into the ansible container), before → after.

Before (without this patch) — reproduces the bug:

TASK [install PMM client rpm packages]
fatal: FAILED! => {"failures": ["No package pmm2-client-2.44.1-6.el9 available."], "msg": "Failed to install some of the specified packages"}

percona-release is installed but no repo enables the pmm2-client package, so yum can't find it.

After (with this patch) — clean pass, and the new task fires:

TASK [enable pmm2-client repo]          ← added by this PR, runs for 2.x on EL
TASK [install PMM client rpm packages]  ← succeeds
TASK [Setup pmm-admin PMM2]
PLAY RECAP  node1 : ok=32  changed=17  failed=0

End-to-end registration against a real percona/pmm-server:2.44.1 also works:

MySQL           node1-mysql   127.0.0.1:3306
pmm_agent       Connected
node_exporter   Running
mysqld_exporter Running
vmagent         Running

The change is correct and minimal — it mirrors the existing enable pmm3-client task with the startswith('2') guard and the pmm2-client repo name; the package-name logic in roles/tools_and_monitoring/vars/main.yml already emitted pmm2-client-…, so this repo-enable step was the only missing piece. Only covers the RHEL/yum path, which is the affected one (Debian/Ubuntu install pmm2-client from direct .deb URLs and were never broken).

Note for release: this touches roles/, so the ansible Docker image needs a rebuild+push for binary-only users — the local-mount that made this testable doesn't apply to them.

LGTM. ✅

[zelmario]

Verified end-to-end on el9 with pmm-client:2.44.1-6: reproduced the failure without the patch and confirmed a clean install + full pmm-admin registration with it. Correct, minimal fix. Approving. (Reminder: rebuild+push the ansible image on release since roles/ changed.)