pycurl.c: eliminate duplicated code in util_write_callback()
pycurl.c: eliminate duplicated code in util_write_callback()

Suggested by Zdenek Pavlas <https://bugzilla.redhat.com/857875#c8>.

pycurl/pycurl,pycurl/pycurl,pycurl/pycurl,p/pycurl-archived,p/pycurl-archived,p/pycurl-archived