fix(ci): prevent grep pipe from failing the diagnostics step (#2170)

grep exits 1 when no match is found. Under bash -e with pipefail, this
would abort the failure-capture step before it finishes, defeating its
purpose. Use grep -m1 with || true to ensure the step always succeeds.

Signed-off-by: Bruno Verachten <gounthar@gmail.com>

Author: gounthar

.github/workflows/plugin_update.yml

@@ -81,5 +81,5 @@ jobs:
           echo "=== Container status ==="
           docker ps -a
           echo "=== Jenkins controller logs ==="
-          CTRL=$(docker ps -a --format "{{.Names}}" | grep controller | head -1)
+          CTRL=$(docker ps -a --format "{{.Names}}" | grep -m1 controller || true)
           [ -n "$CTRL" ] && docker logs "$CTRL" 2>&1 | tail -200 || echo "No controller container found"