For some proxies exception "java.net.ProtocolException: Server redirected too many times" might mean incorrect username or password.
Can SonarQube run in HTTPS mode
No. But you can run SonarQube in a standard HTTPS infrastructure using reverse proxy (in this case the reverse proxy must be configured to set the value "X_FORWARDED_PROTO: https" in each HTTP request header. Without this property, redirection initiated by the SonarQube server will fall back on HTTP).
What is the difference between org.codehaus.mojo:sonar-maven-plugin and org.codehaus.sonar:sonar-maven-plugin?