.travis.yml: add --disable-user with the rest of the disables

As all the disabled features only affect system emulation we might as
well disable user mode to save compile time.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

.travis.yml

@@ -52,7 +52,7 @@ env:
     - CONFIG="--disable-system"
     - CONFIG="--disable-user"
     - CONFIG="--enable-debug --enable-debug-tcg"
-    - CONFIG="--disable-linux-aio --disable-cap-ng --disable-attr --disable-brlapi --disable-uuid --disable-libusb"
+    - CONFIG="--disable-linux-aio --disable-cap-ng --disable-attr --disable-brlapi --disable-uuid --disable-libusb --disable-user"
     - CONFIG="--enable-modules --disable-linux-user"
     - CONFIG="--with-coroutine=ucontext --disable-linux-user"
     - CONFIG="--with-coroutine=sigaltstack --disable-linux-user"