The wait_for_header setting return a float instead of an integer

[galphanet]

When setting the wait_for_header, the result is in the form of a float (for example: 3247.4306001663)

When we set wait_for_header: 'Retry-After', the Retry-After should be an integer (see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After)

The problem is that the getWaitForInSeconds() function returns the float. The proposed fix is to round() the result of the getWaitForInSeconds() function in the HeaderStrategy.