Clean up eventlet monkey patch comment and reno

This is a follow up to I887a06566dcc2f09875f975f1e12ae4ff75fd348.

The release note tense is fixed, and more information is added about why
the change was necessary.

Change-Id: Ie89e21460a4a7654795830bf4781404ec506a52f

ironic/cmd/__init__.py

@@ -13,8 +13,10 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-# NOTE(yuriyz): Do eventlet monkey patching here, not in ironic/__init__.py
-# This allows API service runs under Apache.
+# NOTE(yuriyz): Do eventlet monkey patching here, instead of in
+# ironic/__init__.py.  This allows the API service to run without monkey
+# patching under Apache (which uses its own concurrency model). Mixing
+# concurrency models can cause undefined behavior and potentially API timeouts.
 import os
 
 os.environ['EVENTLET_NO_GREENDNS'] = 'yes'

releasenotes/notes/apache-multiple-workers-11d4ba52c89a13e3.yaml

@@ -1,3 +1,5 @@
 ---
 fixes:
-  - Fix issue with multiple threads when ironic API service runs under Apache.
+  - Fixes an issue with requests to the ironic API service sometimes timing
+    out when running under Apache. This was due to mixing two concurrency
+    models (for handling multiple threads).