Up/Down arrows on home page listing regions can look like smudges; needs definition

This has come up a few times now on branch-2.1 votes: http://mail-archives.apache.org/mod_mbox/hbase-dev/201810.mbox/%3CCAAAYAnPJCJzSb+yneFeCZp4pk9XgXxEcW+PnpppVU6_oGoejSA@mail.gmail.com%3E and then later by our dbist13 votiing on a 2.1.2RC (Artem added an image here: https://photos.app.goo.gl/PziWBMAzXCwbZqmF8). The UI got a bit of more detail added around region transitioning and it cluttered the UI such that the up/down sort arrows can look crowded.