Add ability to create DontFragmentAttribute attribute from a factory

[sdubov]

No description provided.

[jitsi-jenkins]

Hi, thanks for your contribution!
If you haven't already done so, could you please make sure you sign our CLA (https://jitsi.org/icla for individuals and https://jitsi.org/ccla for corporations)? We would unfortunately be unable to merge your patch unless we have that piece :(.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 38.75%. Comparing base (64a7ca8) to head (2d196ef).
⚠️ Report is 44 commits behind head on master.

Files with missing lines	Patch %	Lines
...ain/java/org/ice4j/attribute/AttributeFactory.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #243      +/-   ##
============================================
+ Coverage     38.60%   38.75%   +0.15%     
- Complexity     1351     1355       +4     
============================================
  Files           178      178              
  Lines         12142    12144       +2     
  Branches       1836     1836              
============================================
+ Hits           4688     4707      +19     
+ Misses         6802     6788      -14     
+ Partials        652      649       -3     

Files with missing lines	Coverage Δ
...ain/java/org/ice4j/attribute/AttributeFactory.java	42.85% <0.00%> (-0.74%)	⬇️

... and 13 files with indirect coverage changes

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