Add update_only parameter for yum module (#22206)

* Add update_only parameter for yum module

When using latest, `update_only: yes` will ensure that only existing
packages are updated and no additional packages are installed.

* Update yum.py

Update version added for `update_only` parameter to 2.5

* add unit tests for update_only flag in yum module

test/integration/targets/yum/tasks/yum.yml

@@ -427,3 +427,32 @@
     that:
         - "'changed' in yum_result"
         - "'msg' in yum_result"
+
+- name: use latest to install httpd
+  yum:
+    name: httpd
+    state: latest
+  register: yum_result
+
+- name: verify httpd was installed
+  assert:
+    that:
+      - "'changed' in yum_result"
+
+- name: uninstall httpd
+  yum:
+    name: httpd
+    state: removed
+
+- name: update httpd only if it exists
+  yum:
+    name: httpd
+    state: latest
+    update_only: yes
+  register: yum_result
+
+- name: verify httpd not installed
+  assert:
+    that:
+      - "not yum_result.changed"
+      - "'Packages providing httpd not installed due to update_only specified' in yum_result.results"