[SPARK-2981][GraphX] EdgePartition1D Int overflow

minor fix
detail is here: https://issues.apache.org/jira/browse/SPARK-2981

Author: Larry Xiao <xiaodi@sjtu.edu.cn>

Closes #1902 from larryxiao/2981 and squashes the following commits:

88059a2 [Larry Xiao] [SPARK-2981][GraphX] EdgePartition1D Int overflow

graphx/src/main/scala/org/apache/spark/graphx/PartitionStrategy.scala

@@ -91,7 +91,7 @@ object PartitionStrategy {
   case object EdgePartition1D extends PartitionStrategy {
     override def getPartition(src: VertexId, dst: VertexId, numParts: PartitionID): PartitionID = {
       val mixingPrime: VertexId = 1125899906842597L
-      (math.abs(src) * mixingPrime).toInt % numParts
+      (math.abs(src * mixingPrime) % numParts).toInt
     }
   }