ceph-dashboard: fix TLS cert openssl generation

ceph-dashboard: fix TLS cert openssl generation

With OpenSSL version prior 1.1.1 (like CentOS 7 with 1.0.2k), the -addext
doesn't exist.
As a solution, this uses the default openssl.cnf configuration file as a
template and add the subjectAltName in the v3_ca section. This temp openssl
configuration file is removed after the TLS certificate creation.
This patch also move the run_once statement at the block level.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1978869
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>
(cherry picked from commit 5e0ace7e5493f7d8299155e915435691a0f1a007)