Fix -E parameter conflict with AAD authentication

When no username is passed to the sqlserver connection URL, the adapter adds the -E parameter to the sqlcmd command. However, when using ActiveDirectoryDefault in the --authentication-method parameter, it doesn't work because the go-sqlcmd program will choose integrated authentication instead of AAD authentication. Integrated authentication is chosen in go-sqlcmd either because the -E parameter is provided or because the username is empty and the authentication method is not specified. This commit prevents the -E parameter from being passed if the authentication method parameter is provided, ensuring that AAD authentication can be used properly.