code before:
VC_REAL_TIME_SAMPLING_INTERVAL = 20
samples_cnt = (int(duration / VC_REAL_TIME_SAMPLING_INTERVAL)
if duration else 1)
query_spec.maxSample = samples_cnt
if we set the value of "interval" in /etc/ceilometer/pipline.yaml to less
than 20,the value of "query_spec.maxSample" will be 0,which will cause
problem when use it to send request to vsphere server
Change-Id: Ibdb586109fe5334f3080539a40ff92badead837b
Closes-Bug:#1415307