Sumologic update

[msuterski]

This fixes a problem where changes to existing sumologic definition would not be pushed to Fastly.

[msuterski]

@thommahoney I was wondering if this could be reviewed. We're bumping into this problem all over again.

Thanks

[jrynyt]

this also prevents adding a new sumologic configuration to an existing fastly service.

[thommahoney]

Thanks for fixing this!