tidb-server:Remove the override of GOMAXPROCS (#5567)
tidb-server:Remove the override of GOMAXPROCS (#5567)

From Go 1.5, the default setting of GOMAXPROCS is the number of
CPUs available, and we need 1.9 or above now. we might as well
remove this so people can set GOMAXPROCS to a custom value using
environment variables.
kyle-wang/tidb,qiuyesuifeng/tidb,ngaut/tidb,CodeRushing/tidb,mccxj/tidb,kyle-wang/tidb,pingcap/tidb,coocood/tidb,pingcap/tidb,Cofyc/tidb,yangwenmai/tidb,ngaut/tidb,Cofyc/tidb,kyle-wang/tidb,pingcap/tidb,mccxj/tidb,XuHuaiyu/tidb,kyle-wang/tidb,ngaut/tidb,kyle-wang/tidb,pingcap/tidb,wusphinx/tidb,ngaut/tidb,c4pt0r/tidb,c4pt0r/tidb,spongedu/tidb,qiuyesuifeng/tidb,c4pt0r/tidb,wusphinx/tidb,spongedu/tidb,ming-relax/tidb,cosmtrek/tidb,EvilMcJerkface/tidb,CodeRushing/tidb,ngaut/tidb,cosmtrek/tidb,ngaut/tidb,kyle-wang/tidb,EvilMcJerkface/tidb,Nify/tidb,c4pt0r/tidb,coocood/tidb,c4pt0r/tidb,XuHuaiyu/tidb,pingcap/tidb,tiancaiamao/tidb,tiancaiamao/tidb,Nify/tidb,yangwenmai/tidb,ming-relax/tidb,pingcap/tidb,c4pt0r/tidb