Fix Maven deployment, and remove/hide warning

Shell script in Jenkins exits at first error (as if 'set -e'), and
condition for conditionally (sic!) deleting META-INF/INDEX.LIST from
JARS was inverted.
Also redirect the condition output to /dev/null for a cleaner script
output.

Finally, also use a similar condition for creating sources JARs to
avoid a 'Nothing to do!' warning on console for gwt-servlet, which
doesn't contain source files.

Change-Id: I20af084619bc6044cfa68d9e6ca328a20f84b476
diff --git a/maven/lib-gwt.sh b/maven/lib-gwt.sh
index 4d571d6..b6dac82 100644
--- a/maven/lib-gwt.sh
+++ b/maven/lib-gwt.sh
@@ -123,13 +123,15 @@
 
     # Get rid of the INDEX.LIST file, since it's going to be out of date
     # once we rename the jar files for Maven
-    if ! unzip -lqq $CUR_FILE META-INF/INDEX.LIST; then
+    if unzip -l $CUR_FILE META-INF/INDEX.LIST >/dev/null; then
       echo "Removing INDEX.LIST from gwt-${i}"
       zip -d $CUR_FILE META-INF/INDEX.LIST
     fi
 
     SOURCES_FILE=$GWT_EXTRACT_DIR/gwt-${i}-sources.jar
-    zip -q $CUR_FILE --copy --out $SOURCES_FILE "*.java"
+    if unzip -l $CUR_FILE '*.java' >/dev/null; then
+      zip -q $CUR_FILE --copy --out $SOURCES_FILE "*.java"
+    fi
   done
 
   # push parent poms