Description of problem:
When I move cursor over timelines view in vertical direction, I can notice blinking vertical bar and timestamp. Actually, it blinks only for a moment and I can make out the timestamp numbers. Additionally, it appears only when I quickly move mouse pointer in vertical direction.
So, current behavior of this control is useless and annoying.

Version-Release number of selected component (if applicable):
5.7.0.9

How reproducible:
100

Steps to Reproduce:
1. Add Infra provider f.e. vsphere55.
2. Do something within provider. f.e. deploy/start/stop vm
3. Open Timelines for provider
4. Select all management categories and choose centered position
5. Click Apply button
6. put mouse pointer over timelines view and move it in vertical direction to the top or bottom. pay attention on the control behavior 

Actual results:
1.the control's bar is displayed only when mouse pointer is quickly moved in vertical direction.
2. it is difficult to make out what timestamp is displayed
3. both bar and timestamp are always blinking

Expected results:
In my opinion, this control should behave in the following way:
1. it should always be displayed
2. it shouldn't blink