graph_draw(): Fix inline SVG drawing with jupyter notebooks

This fixes issue #469
6 jobs for master in 203 minutes and 38 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #3598
amd64
job_clang_amd64

03:17:28

passed #3602
amd64
job_clang_amd64_nosh

02:56:30

passed #3600
amd64
job_clang_py2_amd64

03:23:38

passed #3597
amd64
job_gcc_amd64

02:44:24

passed #3601
amd64
job_gcc_amd64_nosh

02:07:32

passed #3599
amd64
job_gcc_py2_amd64

02:40:37