gem_module: Update Integration tests for bindir option

Make sure gist is not installed system-wide prior the tests

tests/integration/targets/gem/tasks/main.yml

@@ -180,6 +180,12 @@
       - gem_search.files | length == 0
 
 # Custom directory for executables (--bindir)
+- name: Ensure gem is not installed
+  gem:
+    name: gist
+    state: absent
+    user_install: no  # Avoid conflicts between --install-dir and --user-install when running as root on CentOS / Fedora / RHEL
+
 - name: Install gem with custom bindir
   gem:
     name: gist