[ci] Switch glusterfs-nfs job to focal fossa

Depends-On: https://review.opendev.org/762613
Change-Id: Ia25a49bb35dae62a045eaad9a86b5192141fb32b
Partial-Bug: #1896672
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>
1 file changed