Updates .gitignore
Updates .gitignore

To ignore swap files from getting into repository
currently the implemented ignores are *.swp and *.swo
however vim adds more swap files if these files exists,
so improving this with *.sw?

Change-Id: Ie1b458d2b862e6cf2552ae5be6c6178b72e960ab
Closes-Bug: #1255876

Tehsmash/networking-cisco-apic,Tehsmash/networking-cisco-nexus