CB-5762 android: Fix lengthComputable set wrong for gzip downloads

Gzip + no Content-Length header should be lengthComputable=false

src/android/FileTransfer.java

@@ -760,9 +760,11 @@ public class FileTransfer extends CordovaPlugin {
                         if (connection.getContentEncoding() == null || connection.getContentEncoding().equalsIgnoreCase("gzip")) {
                             // Only trust content-length header if we understand
                             // the encoding -- identity or gzip
+                            if (connection.getContentLength() != -1) {
                                 progress.setLengthComputable(true);
                                 progress.setTotal(connection.getContentLength());
                             }
+                        }
                         inputStream = getInputStream(connection);
                     }