tests: limit HEAD requests to 30s
There should not be needed more than few seconds to contact a server, and start a HEAD request to check for the existence of a URL. Considering that requests does not have a default timeout, limit it ourselves to 30 seconds: this is generous enough to account for network slowness, a busy remote server, or a slow test environment, without potentially stalling for a long time.
Signed-off-by: Pino Toscano ptoscano@redhat.com