cmd/callgraph: fix careless quoting bug
cmd/callgraph: fix careless quoting bug

Change-Id: I809a2ea711bb1a516dfcf8abf5e4d26061b4daf0
Reviewed-on: https://go-review.googlesource.com/4230
Reviewed-by: Sameer Ajmani <da4a4efb907a17fabb3e092841511e7f24e226cf@golang.org>

cmars/tools,dmitris/tools,cmars/tools,glasser/golang-tools,glasser/golang-tools,glasser/golang-tools,cmars/tools,jdhenke/tools,nicot/tools,runcom/tools,runcom/tools,golang/tools,jdhenke/tools,nicot/tools,springning/tools,sshetty10/tools,magiccao/tools,cw2018/tools,dmitris/tools,springning/tools,cmars/tools,syreclabs/go-tools,josharian/tools,josharian/tools,josharian/tools,syreclabs/go-tools,springning/tools,magiccao/tools,runcom/tools,matryer/tools,golang/tools,sshetty10/tools,magiccao/tools,cw2018/tools,sshetty10/tools,cw2018/tools,matryer/tools,magiccao/tools,syreclabs/go-tools,argandas/tools,golang/tools,golang/tools,springning/tools,josharian/tools,argandas/tools,nicot/tools,syreclabs/go-tools,runcom/tools,nicot/tools,matryer/tools,sshetty10/tools,syreclabs/go-tools,glasser/golang-tools,golang/tools,matryer/tools,dmitris/tools,jdhenke/tools,syreclabs/go-tools,jdhenke/tools,cw2018/tools,argandas/tools,argandas/tools,dmitris/tools