Add return false to supports_checksum for svn fetcher which fhis
fixes MIRROR usage for svn uris. Also add a testcase.
[YOCTO #15473]
(Bitbake rev: 21cfc7ae9a19f39ac8904e1c3466e7e499ac523f)
Signed-off-by: Kari Sivonen <kari.sivonen@live.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>