Updates .gitignore to ignore *.egg*

Reasons:
 - pbr-*.egg* is created during tox testing
 - To ignore any package being generated in future

Changes:
 - *.egg* is added in .gitignore
 - python_troveclient.egg* is removed as *.egg*
   takes care of this too.

Change-Id: Ib66bdca8d8d632e88e22cc533d7591613b87123b
Closes-Bug: #1259221
Merge "Updates .gitignore to ignore *.egg*"