CE badge performance improvement

[pawlakm]

the request can be improved by using parameter "onlyCurrents" (which make the WS do way less SQL requests):

• this parameter only returns tasks of the past (not from the queue) and only the latest one
• the plugin does only care about the most recent task (and the WS will return only one task with this parameter on)
• the plugin doesn't care about the queue (in fact it does not specify the "status" parameter, which value is by default is SUCCESS,FAILED,CANCELED (see https://sonarqube.com/web_api/api/ce/activity)), ie. statuses of past tasks

Note: this issue was reported by SonarQube team, thank you.