fix(tooltip): flickering when hover the mouse

[tarusin]

PR Checklist

Before creating new PR, please take a look at checklist below to make sure that you've done everything that needs to be done before we can merge it.

• read and followed the CONTRIBUTING.md guide.
• built and tested the changes locally.
• added/updated tests.
• added/updated API documentation.
• added/updated demos.

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Issue: #3075

[codecov]

Codecov Report

Merging #4660 into development will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           development    #4660   +/-   ##
============================================
  Coverage        71.44%   71.44%           
============================================
  Files              259      259           
  Lines             8378     8378           
  Branches          1562     1562           
============================================
  Hits              5986     5986           
  Misses            1985     1985           
  Partials           407      407

Impacted Files	Coverage Δ
src/tooltip/tooltip-container.component.ts	76.47% <ø> (ø)	⬆️

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[OlegDubrovskyi]

Looks good.
Tested on IE11, Edge, Chrome 68, Firefox 61