qa/workunits/cephadm/test_cephadm: add SUDO to `vgchange`

qa/workunits/cephadm/test_cephadm: add SUDO to `vgchange`

2020-01-13T10:48:14.235 INFO:tasks.workunit.client.0.smithi177.stderr:+ vgchange -an test_cephadm
2020-01-13T10:48:14.239 INFO:tasks.workunit.client.0.smithi177.stderr:  WARNING: Running as a non-root user. Functionality may be unavailable.
2020-01-13T10:48:14.239 INFO:tasks.workunit.client.0.smithi177.stderr:  /run/lvm/lvmetad.socket: access failed: Permission denied
2020-01-13T10:48:14.240 INFO:tasks.workunit.client.0.smithi177.stderr:  WARNING: Failed to connect to lvmetad. Falling back to device scanning.
2020-01-13T10:48:14.260 INFO:tasks.workunit.client.0.smithi177.stderr:  /dev/mapper/control: open failed: Permission denied
2020-01-13T10:48:14.261 INFO:tasks.workunit.client.0.smithi177.stderr:  Failure to communicate with kernel device-mapper driver.
2020-01-13T10:48:14.261 INFO:tasks.workunit.client.0.smithi177.stderr:  Incompatible libdevmapper 1.02.145 (2017-11-03) and kernel driver (unknown version).
2020-01-13T10:48:14.301 INFO:tasks.workunit.client.0.smithi177.stderr:  /run/lock/lvm/V_test_cephadm:aux: open failed: Permission denied
2020-01-13T10:48:14.301 INFO:tasks.workunit.client.0.smithi177.stderr:  Can't get lock for test_cephadm
2020-01-13T10:48:14.301 INFO:tasks.workunit.client.0.smithi177.stderr:  Cannot process volume group test_cephadm

Signed-off-by: Michael Fritch <mfritch@suse.com>