Merge pull request #4441 from tensor-tang/develop

should reset env every time

benchmark/paddle/image/run_mkldnn.sh

 set -e
 
-unset OMP_NUM_THREADS MKL_NUM_THREADS
-export OMP_DYNAMIC="FALSE"
-export KMP_AFFINITY="granularity=fine,compact,0,0"
-
 function train() {
+  unset OMP_NUM_THREADS MKL_NUM_THREADS
+  export OMP_DYNAMIC="FALSE"
+  export KMP_AFFINITY="granularity=fine,compact,0,0"
   topology=$1
   bs=$2
   use_mkldnn=$3