fix(gesture): 'drag' gestures don't clean up touch action styles on parent

[Splaktar]

PR Checklist

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• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
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PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Touch action styles are applied by $mdGesture.register(x, 'drag'); but they are not cleaned up on deregister if there was no touch action style previously on the element.

Before bottom sheet opened

<div class="ng-scope">

After bottom sheet opened

<div class="ng-scope" style="touch-action: pan-x;">

After bottom sheet closed

<div class="ng-scope" style="touch-action: pan-x;">

Issue Number:
Fixes #11147

What is the new behavior?

Touch action styles are applied by $mdGesture.register(x, 'drag'); and they are cleaned up on deregister, even if there was no touch action style previously on the element.

Before bottom sheet opened

<div class="ng-scope">

After bottom sheet opened

<div class="ng-scope" style="touch-action: pan-x;">

After bottom sheet closed

<div class="ng-scope" style>

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[mmalerba]

LGTM