cputest: Add data for Intel(R) Xeon(R) CPU E5-2623 v4

cputest: Add data for Intel(R) Xeon(R) CPU E5-2623 v4

The CPU contains the updated microcode for CVE-2017-5715.

The *-guest.xml and *-json.xml CPU definitions use Skylake-Client CPU
model rather than Broadwell. This is similar to Xeon-E5-2650-v4 and it
is caused by our CPU model selection code when no model matches the CPU
signature (family + model). We'd need to maintain a complete list of CPU
signatures for our CPU models to fix this.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>