Correct package name used in version info

pbr uses importlib_metadata which uses distribution package name
(python-jenkins) to get version.
The old wrong code will get version of https://pypi.org/project/jenkins,
or generate a wrong version in packaing if not in the python-jenkins Git
repo.

Change-Id: I37e1c0e5e3b6aea249333e24001c58f47e81a83e

jenkins/version.py

@@ -17,4 +17,4 @@
 
 import pbr.version
 
-version_info = pbr.version.VersionInfo('jenkins')
+version_info = pbr.version.VersionInfo('python-jenkins')