Fix minor codestyle issues

smack-experimental/src/test/java/org/jivesoftware/smackx/httpfileupload/FileTooLargeErrorCreateTest.java

@@ -22,7 +22,7 @@ import org.junit.Assert;
 import org.junit.Test;
 
 public class FileTooLargeErrorCreateTest {
-    String fileTooLargeErrorExtensionExample
+    private static final String fileTooLargeErrorExtensionExample
             = "<file-too-large xmlns='urn:xmpp:http:upload:0'>"
             +   "<max-file-size>20000</max-file-size>"
             + "</file-too-large>";

smack-experimental/src/test/java/org/jivesoftware/smackx/httpfileupload/SlotCreateTest.java

@@ -28,7 +28,7 @@ import org.junit.Test;
 import org.xml.sax.SAXException;
 
 public class SlotCreateTest {
-    String testSlot
+    private static final String testSlot
             = "<slot xmlns='urn:xmpp:http:upload:0'>"
             +     "<put url='https://upload.montague.tld/4a771ac1-f0b2-4a4a-9700-f2a26fa2bb67/my_juliet.png'></put>"
             +     "<get url='https://download.montague.tld/4a771ac1-f0b2-4a4a-9700-f2a26fa2bb67/my_juliet.png'></get>"

smack-experimental/src/test/java/org/jivesoftware/smackx/httpfileupload/SlotRequestCreateTest.java

@@ -29,14 +29,14 @@ import org.xml.sax.SAXException;
 
 public class SlotRequestCreateTest {
 
-    String testRequest
+    private static final String testRequest
             = "<request xmlns='urn:xmpp:http:upload:0'"
             +   " filename='my_juliet.png'"
             +   " size='23456'"
             +   " content-type='image/jpeg'"
             + "/>";
 
-    String testRequestWithoutContentType
+    private static final String testRequestWithoutContentType
             = "<request xmlns='urn:xmpp:http:upload:0'"
             +   " filename='my_romeo.png'"
             +   " size='52523'"

smack-experimental/src/test/java/org/jivesoftware/smackx/httpfileupload/provider/FileTooLargeErrorProviderTest.java

@@ -30,7 +30,7 @@ public class FileTooLargeErrorProviderTest {
      * Example 7. Alternative response by the upload service if the file size was too large
      * @see <a href="http://xmpp.org/extensions/xep-0363.html#errors">XEP-0363: HTTP File Upload 5. Error conditions</a>
      */
-    String slotErrorFileToLarge
+    private static final String slotErrorFileToLarge
             = "<iq from='upload.montague.tld' "
             +       "id='step_03' "
             +       "to='romeo@montague.tld/garden' "