Add libgcrypt to RedHat dependencies

CentOS 8.3 has a bug in which updating qemu-kvm does not update
libgcrypt. This leads to failues when using libvirt/qemu. It seems to
happen on CentOS 8.2 images, since the 8.3 packages became available See
https://bugzilla.redhat.com/show_bug.cgi?id=1840485.

Fixes: #42

Author: markgoddard

vars/RedHat.yml

@@ -1,6 +1,10 @@
 ---
 # List of libvirt package dependencies.
 libvirt_host_libvirt_packages_default:
+  # NOTE(mgoddard): CentOS 8.3 has a bug in which updating qemu-kvm does not
+  # update libgcrypt. This leads to failues when using libvirt/qemu. See
+  # https://bugzilla.redhat.com/show_bug.cgi?id=1840485.
+  - libgcrypt
   - libvirt
   - libvirt-daemon-kvm
   - "{{ 'python3-libvirt' if libvirt_host_python3 | bool else 'libvirt-python' }}"