PullRequest: added reset and clean after merge or attemptMerge
PullRequest: added reset and clean after merge or attemptMerge

When a pull-request did merge or attemptMerge operation, it was possible that there remains untracked file.
Because of it, the pull-request's repository couldn't move to other branch.
This causes non-stop waiting status and pull-request form error.

So I've added git reset and git clean operation after attemptMerge or merge.

bloodybear/yona,brainagenet/yobi,oolso/yobi,brainagenet/yobi,Limseunghwan/oss,ChangsungKim/TestRepository01,violetag/demo,bloodybear/yona,doortts/fork-yobi,doortts/fork-yobi,naver/yobi,violetag/demo,ihoneymon/yobi,oolso/yobi,doortts/fork-yobi,ahb0327/yobi,doortts/fork-yobi,oolso/yobi,ahb0327/yobi,brainagenet/yobi,ihoneymon/yobi,yona-projects/yona,Limseunghwan/oss,ahb0327/yobi,bloodybear/yona,yona-projects/yona,Limseunghwan/oss,bloodybear/yona,yona-projects/yona,naver/yobi,doortts/forked-for-history,ChangsungKim/TestRepository01,doortts/forked-for-history,doortts/forked-for-history,naver/yobi,ihoneymon/yobi,yona-projects/yona