xl/zones: return errNoHealRequired when no heal is required (#8821)

Zone abstraction of object layer was returning `nil`
incorrectly under situations where disk healing is
not required. Returning `nil` is considered as healing
successful, which leads to unexpected ReloadFormat()
peer notification calls during startup.

This PR fixes this behavior properly for zones.

mint/build/aws-sdk-java/build.xml

@@ -9,7 +9,7 @@
 
     <target name="download-ivy" unless="offline">
         <mkdir dir="${ivy.jar.dir}"/>
-        <get src="https://repo1.maven.org/maven2/org/apache/ivy/ivy/${ivy.install.version}/ivy-${ivy.install.version}.jar" 
+        <get src="https://repo1.maven.org/maven2/org/apache/ivy/ivy/${ivy.install.version}/ivy-${ivy.install.version}.jar"
              dest="${ivy.jar.file}" usetimestamp="true"/>
     </target>