Clean lock before and after conda create

ci/bootstrap.sh

@@ -56,6 +56,7 @@ if [ ! -d ${PREFIX} ]; then
   pyver=$(echo ${PYTHON_VERSION} | tr -d '.')
   curl --silent https://gitlab.idiap.ch/bob/bob.admin/raw/master/install/${ARCH}/devel-py${pyver}.txt > env.txt
   yellow_echo "[++] Bootstrapping conda installation at ${PREFIX}..."
+  run_cmd ${CONDA_FOLDER}/bin/conda clean --lock
   run_cmd ${CONDA_FOLDER}/bin/conda create --prefix ${PREFIX} --file env.txt --yes
 
   # Dirty fix to libjpeg.8 compilation issues: