Fix CentOS 7 CI test job failures because of zero sized /etc/machine-id
Fragment from the first commit message ...
Since August 2020, GitLab Continuous Integration test jobs have been failing on the CentOS 7 image like this from tests/test_SupportedFileSystems.log:
process 6319: D-Bus library appears to be incorrectly set up; failed to read machine uuid: UUID file '/etc/machine-id' should contain a hex string of length 32, not length 0, with no other text See the manual page for dbus-uuidgen to correct this issue. D-Bus not built with -rdynamic so unable to print a backtrace Running main() from test_SupportedFileSystems.cc DISPLAY=":99" /usr/bin/xvfb-run: line 181: 6319 Aborted (core dumped) DISPLAY=:$SERVERNUM XAUTHORITY=$AUTHFILE "$@" 2>&1