Fix bugs in bigquery storage driver.
Fix bugs in bigquery storage driver.

digideskio/heapster,dalanlan/heapster,bruceauyeung/heapster,adfin/statster,bluebreezecf/heapster,mdshuai/heapster,thucatebay/heapster,mwringe/heapster,andyxning/heapster,whuwxl/heapster,afein/heapster,fzu-huang/heapster,liubog2008/heapster,bluebreezecf/heapster,fzu-huang/heapster,jimmidyson/heapster,titilambert/heapster,nlamirault/heapster,Huawei-PaaS/heapster,Huawei-PaaS/heapster,jackzampolin/heapster,wulonghui/heapster,saiwl/heapster,jackzampolin/heapster,apeeyush/heapster,aegixx/heapster,vmarmol/heapster,titilambert/heapster,a-robinson/heapster,piosz/heapster,krzyzacy/heapster,AlmogBaku/heapster,burmanm/heapster,ravihansa3000/heapster,vicki-c/heapster,skytap/heapster,relh/heapster,vmarmol/heapster,johanneswuerbach/heapster,naxhh/heapster,relh/heapster,vmarmol/heapster,lavalamp/heapster,taimir/heapster,aegixx/heapster,whuwxl/heapster,skytap/heapster,dalanlan/heapster,rjnagal/heapster,krzyzacy/heapster,piosz/heapster,mwringe/heapster,nlamirault/heapster,thucatebay/heapster,ravihansa3000/heapster,burmanm/heapster,vishh/heapster-1,digideskio/heapster,wulonghui/heapster,jimmidyson/heapster,mwielgus/heapster,liubog2008/heapster,saad-ali/heapster,shilpamayanna/heapster,afein/heapster,lavalamp/heapster,a-robinson/heapster,bruceauyeung/heapster,rjnagal/heapster,saad-ali/heapster,andyxning/heapster,vishh/heapster-1,jfoy/heapster,huangyuqi/heapster,luxas/heapster,liuhewei/heapster,rjnagal/heapster,jszczepkowski/heapster,naxhh/heapster,Stackdriver/heapster,huangyuqi/heapster,johanneswuerbach/heapster,AlmogBaku/heapster,apeeyush/heapster,liuhewei/heapster,luxas/heapster,Stackdriver/heapster,vicki-c/heapster,jfoy/heapster,shilpamayanna/heapster,saiwl/heapster,mdshuai/heapster,taimir/heapster,jszczepkowski/heapster,mwielgus/heapster,adfin/statster