[Timestrip] Zoom and pan are incorrectly disabled for Plot object views contained within a Timestrip

[charlesh88]

Reproduce

1. Create a Timestrip and add numeric telemetry that view as plots. Save the Timestrip.
2. In the tree, expand the Timestrip and navigate to one of the telemetry points. The main view should show a plot view.
3. Mouseover the plot and observe: no zoom buttons are displayed.
4. Try to zoom via dragging a marquee or by using the mousewheel, observe: nothing happens.

This is a side effect of the desire to disable zoom and pan while viewing the Timestrip itself, but has had an undesired effect of suppressing those features for the Timestrip's children's views themselves.

Solution: use CSS pointer-events: none applied to the plot view's .gl-plot-display-area element when within a Timestrip.

[shefalijoshi]

We're disabling gesture controls right now by looking at the objectPath and checking if there is a time strip in that path.
This may not be the best way to disable controls.
https://github.com/nasa/openmct/blob/master/src/plugins/plot/PlotViewProvider.js#L43

The fix might be to check that the current view is a time strip view instead.

[charlesh88]

@shefalijoshi Let me know how you want to proceed. The CSS solution will work I think, but may not be the best practice.

[nikhilmandlik]

Verified Fixed.