travis: Allow vtr to fail for now.
travis: Allow vtr to fail for now.

timvideos/conda-misoc-lm32,litex-hub/litex-conda-prog,timvideos/conda-hdmi2usb-packages,timvideos/conda-misoc-lm32,litex-hub/litex-conda-eda,litex-hub/litex-conda-compilers,timvideos/conda-hdmi2usb-packages