Fetch remotes before switch-branch by default
    
    If new branch was created on remote repository developer would need to
    run both following commands to properly switch:
    
    $ git fetch origin
    $ rhpkg switch-branch $NEW  # or fedpkg switch-branch $NEW
    
    To save typing first command (which could be seen as a completely
    different program) this fix does git fetch automatically.
    
    Previous functionality may be desirable if one doesn't have online
    connection to remote. New option --no-fetch can be used in that case.
    
    Resolves: rhbz#1066522