graphic: adjust test code

- import gocheck with name "C"
- check result image file's md5 hashes in each test case
- disable spare output

Change-Id: Ie1d1b38d8418dbb9fe2228a6d473b12d950ccef2
gdkpixbuf: adjust test code

- import gocheck with name "C"
- check result image file's md5 hashes in each test case
- disable spare output

Change-Id: Ia711a08db47cc2716c93609f1128b0e7da3e8abb
Merge "graphic: adjust test code"