Add Checkstyle SimplifyBooleanReturn

Author: garydgregory

src/conf/checkstyle.xml

@@ -70,6 +70,7 @@ limitations under the License.
       <property name="message" value="Trailing whitespace" />
     </module>
     <module name="SimplifyBooleanExpression" />
+    <module name="SimplifyBooleanReturn" />
     <module name="TypecastParenPad" />
     <module name="UnusedImports" />
     <module name="WhitespaceAfter" />