ci: Fix Mariner rootfs build failure

This implements a workaround for microsoft/azurelinux#13971 to unblock
the CI.

Signed-off-by: Aurélien Bombo <abombo@microsoft.com>

tools/osbuilder/rootfs-builder/cbl-mariner/Dockerfile.in

@@ -11,6 +11,9 @@ RUN tdnf -y install \
     dnf \
     git \
     tar \
-    xz
+    xz \
+    # TODO: Remove when this issue is fixed:
+    # https://github.com/microsoft/azurelinux/issues/13971
+    --exclude=aznfs
 
 @INSTALL_RUST@