Use apache2 reverse proxy instead of mirror

This MR replaces our mirror address used in the CI with a new apache2 caching reverse proxy setup that is more flexible than the mirroring setup.

@bob: please report weird issues related to conda lookups.

bob/devtools/bootstrap.py

@@ -454,13 +454,13 @@ if __name__ == "__main__":
     logger.info("(create) %s", condarc)
     with open(condarc, "wt") as f:
         # Replaces https://repo.anaconda.com/pkgs/main by
-        # http://www.idiap.ch/software/bob/defaults with so it is optimized for
+        # http://bobconda.lab.idiap.ch:8000, so it is optimized for
         # a CI build.  Notice we consider this script is only executed in this
         # context.  The URL should NOT work outside of Idiap's network.
         f.write(
             _BASE_CONDARC.replace(
-                "https://repo.anaconda.com/pkgs/main",
-                "http://www.idiap.ch/defaults",
+                "https://repo.anaconda.com",
+                "http://bobconda.lab.idiap.ch:8000",
             )
         )