Dockerfile: use local openstack-ci-core PPA key

We see timeouts trying to get this key fairly frequently in the gate.
Store it locally and use that in the container build.

Change-Id: Ifd706849f1fad88c8ec4afc79090df4afb88abb4

Dockerfile

@@ -58,11 +58,11 @@ RUN echo "nodepool ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/nodepool-sudo \
 #      https://salsa.debian.org/installer-team/debootstrap/-/merge_requests/26
 #      https://salsa.debian.org/installer-team/debootstrap/-/merge_requests/27
 #    are incoporated into the openstack-ci-core version
+
+COPY tools/openstack-ci-core-ppa.asc /etc/apt/trusted.gpg.d/
+
 RUN \
-  apt-get update \
-  && apt-get install -y gnupg2 \
-  && apt-key adv --keyserver keyserver.ubuntu.com --recv 2B5DE24F0EC9F98BD2F85CA315B6CE7C018D05F5 \
-  && echo "deb http://ppa.launchpad.net/openstack-ci-core/vhd-util/ubuntu bionic main" >> /etc/apt/sources.list \
+  echo "deb http://ppa.launchpad.net/openstack-ci-core/vhd-util/ubuntu bionic main" >> /etc/apt/sources.list \
   && echo "deb http://ppa.launchpad.net/openstack-ci-core/debootstrap/ubuntu focal main" >> /etc/apt/sources.list \
   && apt-get update \
   && apt-get install -y \

tools/openstack-ci-core-ppa.asc

@@ -0,0 +1,28 @@
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+
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+5pX70jigBqjtJ0PZGm7jELb8bB70SVSGsvwHmEz0pSs=
+=d9cr
+-----END PGP PUBLIC KEY BLOCK-----