JSSE: return unmodifiable list from all getRequestedServerNames() paths

Author: cconlon

src/java/com/wolfssl/provider/jsse/WolfSSLImplementSSLSession.java

@@ -1158,7 +1158,7 @@ public synchronized List<SNIServerName> getRequestedServerNames()
                 sniNames.add(sniName);
                 this.sniServerNames = new ArrayList<SNIServerName>(sniNames);
 
-                return sniNames;
+                return Collections.unmodifiableList(sniNames);
             }
         } catch (IllegalArgumentException e) {
             throw new UnsupportedOperationException(e);