RFR: JDK-8210519: build/releaseFile/CheckSource.java failed additional sources found

[Erik Joelsson]

When I added support for git as SCM in the build, I forgot to update the 
test that verifies the release file contents. This patch updates the 
test to also look for hg/git in the SOURCE strings. While there I also 
made the test more strict on the format and less strict when run against 
non Oracle produced builds where we probably shouldn't be making 
assumptions on what extra repositories may be involved and included in 
the SOURCE line.

Bug: https://bugs.openjdk.java.net/browse/JDK-8210519
Webrev: http://cr.openjdk.java.net/~erikj/8210519/webrev.01/

/Erik