fix(mayactl): correct the calculations for volume metrics (#858)
fix(mayactl): correct the calculations for volume metrics (#858)

Fixed the following to match with the metrics returned
from exporter:
- size parameters are already returned in GB
- fix a bug in throughput calculation
- convert latency from ns to ms

Signed-off-by: kmova <6a28dfa88869c0f71365518480e309e6698873e0@openebs.io>
openebs/maya,prateekpandey14/maya,openebs/maya,AmitKumarDas/maya,openebs/maya,prateekpandey14/maya,AmitKumarDas/maya