[AUTOTVM] tweak `sample_int` implementation (#2677)
[AUTOTVM] tweak `sample_int` implementation (#2677)

* check in

* lint

* cleanup

* Update util.py

sxjscience/tvm,Laurawly/tvm-1,Laurawly/tvm-1,dmlc/tvm,Laurawly/tvm-1,sxjscience/tvm,sxjscience/tvm,sxjscience/tvm,sxjscience/tvm,Huyuwei/tvm,tqchen/tvm,dmlc/tvm,Huyuwei/tvm,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,tqchen/tvm,Huyuwei/tvm,Huyuwei/tvm,dmlc/tvm,Huyuwei/tvm,Laurawly/tvm-1,Laurawly/tvm-1,tqchen/tvm,dmlc/tvm,sxjscience/tvm,tqchen/tvm,tqchen/tvm,sxjscience/tvm,sxjscience/tvm,tqchen/tvm,tqchen/tvm,tqchen/tvm,Huyuwei/tvm,Huyuwei/tvm,dmlc/tvm,Huyuwei/tvm,Huyuwei/tvm,dmlc/tvm,sxjscience/tvm,Laurawly/tvm-1,tqchen/tvm,dmlc/tvm,tqchen/tvm,Laurawly/tvm-1,dmlc/tvm,dmlc/tvm