Fix Giraph-related environment variable
Fix Giraph-related environment variable

The hadoop-gremlin module's Giraph backend requires a certain
environment variable that points to a colon-delimited list of jars or
directories containing jars that will be made available to the Giraph
job executed via MR.  This commit updates that environment variable in
gremlin.sh to point to lib.

mbrukman/titan,graben1437/titan,amcp/titan,CYPP/titan,pluradj/titan,mbrukman/titan,dylanht/titan,banjiewen/titan,englishtown/titan,banjiewen/titan,pluradj/titan,amcp/titan,elubow/titan,amcp/titan,dylanht/titan,CYPP/titan,CYPP/titan,graben1437/titan,elubow/titan,dylanht/titan,banjiewen/titan,mbrukman/titan,englishtown/titan,CYPP/titan,dylanht/titan,thinkaurelius/titan,samanalysis/titan,graben1437/titan,elubow/titan,englishtown/titan,englishtown/titan,thinkaurelius/titan,samanalysis/titan,elubow/titan,pluradj/titan,mbrukman/titan,samanalysis/titan,amcp/titan,graben1437/titan,banjiewen/titan,thinkaurelius/titan,thinkaurelius/titan,mbrukman/titan,samanalysis/titan,pluradj/titan