Set loglevel for signalR to warn

[eivindsjovold]

Ready for review checklist:

• A self-review has been performed
• All commits run individually
• Temporary changes have been removed, like console.log, TODO, etc.
• The PR has been tested locally
• A test has been written
  • This change doesn't need a new test
• Relevant issues are linked
• Remaining work is documented in issues
  • There is no remaining work from this PR that require new issues
• The changes does not introduce dead code as unused imports, functions etc.