rpmbuild, common: always set 'requests.get()' timeout
    
    From https://docs.python-requests.org/en/latest/user/quickstart/#timeouts
    
    | You can tell Requests to stop waiting for a response after a given
    | number of seconds with the timeout parameter. Nearly all production
    | code should use this parameter in nearly all requests. Failure to do
    | so can cause your program to hang indefinitely.
    
    We already use the 'stream=True' additional argument in get() methods,
    so I rather added the **kwargs boilerplate to all of the SafeRequest
    methods.
    
    Fixes: rhbz#2016861