OF-546: Exclude Avalon from Proxool

The Avalon framework is a dependency of the Proxool Maven artificat, but was
never included as a library to Openfire prior the move to Maven (so, we can
do without).

The Avalon dependency itself has a dependency of servlet-api 2.3, which is
unwanted, and causes issues when compiling JSPs.

xmppserver/pom.xml

@@ -266,6 +266,11 @@
                     <groupId>commons-logging</groupId>
                     <artifactId>commons-logging</artifactId>
                 </exclusion>
+                <exclusion>
+                    <!-- This wasn not included prior to the Mavenization of Openfire, and pulls in an unwanted old servlet API. -->
+                    <groupId>avalon-framework</groupId>
+                    <artifactId>avalon-framework-api</artifactId>
+                </exclusion>
             </exclusions>
         </dependency>
         <dependency>