delete unused import,change exit number to -1
delete unused import,change exit number to -1

kumarrus/voltdb,paulmartel/voltdb,wolffcm/voltdb,kobronson/cs-voltdb,ingted/voltdb,flybird119/voltdb,migue/voltdb,deerwalk/voltdb,simonzhangsm/voltdb,kumarrus/voltdb,VoltDB/voltdb,paulmartel/voltdb,flybird119/voltdb,simonzhangsm/voltdb,creative-quant/voltdb,kumarrus/voltdb,migue/voltdb,kobronson/cs-voltdb,simonzhangsm/voltdb,VoltDB/voltdb,creative-quant/voltdb,wolffcm/voltdb,migue/voltdb,paulmartel/voltdb,paulmartel/voltdb,kobronson/cs-voltdb,creative-quant/voltdb,ingted/voltdb,ingted/voltdb,kobronson/cs-voltdb,kobronson/cs-voltdb,creative-quant/voltdb,deerwalk/voltdb,kumarrus/voltdb,kumarrus/voltdb,migue/voltdb,zuowang/voltdb,zuowang/voltdb,migue/voltdb,paulmartel/voltdb,wolffcm/voltdb,ingted/voltdb,wolffcm/voltdb,kumarrus/voltdb,deerwalk/voltdb,VoltDB/voltdb,creative-quant/voltdb,kobronson/cs-voltdb,simonzhangsm/voltdb,zuowang/voltdb,flybird119/voltdb,flybird119/voltdb,deerwalk/voltdb,migue/voltdb,creative-quant/voltdb,VoltDB/voltdb,deerwalk/voltdb,ingted/voltdb,deerwalk/voltdb,simonzhangsm/voltdb,wolffcm/voltdb,deerwalk/voltdb,flybird119/voltdb,zuowang/voltdb,paulmartel/voltdb,ingted/voltdb,wolffcm/voltdb,zuowang/voltdb,creative-quant/voltdb,VoltDB/voltdb,kobronson/cs-voltdb,ingted/voltdb,simonzhangsm/voltdb,flybird119/voltdb,deerwalk/voltdb,VoltDB/voltdb,creative-quant/voltdb,zuowang/voltdb,wolffcm/voltdb,VoltDB/voltdb,simonzhangsm/voltdb,migue/voltdb,flybird119/voltdb,paulmartel/voltdb,kumarrus/voltdb,flybird119/voltdb,migue/voltdb,zuowang/voltdb,kobronson/cs-voltdb,wolffcm/voltdb,kumarrus/voltdb,paulmartel/voltdb,simonzhangsm/voltdb,zuowang/voltdb,ingted/voltdb