remove .cvsignore files, add *.pyc and *.pyo to .gitignore
vsftpd.conf: add background=no to allow for proper shutdown

When the "background" directive in the vsftpd.conf configuration file is
set to "YES", the vsftpd startup script forks, creating a child process
(the vsftpd daemon) which immediately sends the SIGUSR1 signal to its
parent process, which exits upon receiving it.  The teardown routine in
procmgr.py would then send the SIGTERM signal to a process that does not
exist anymore.
pycurl.c: eliminate duplicated code in util_write_callback()

Suggested by Zdenek Pavlas <https://bugzilla.redhat.com/857875#c8>.
pycurl.c: allow to return -1 from write callback

... to abort the transfer and WRITEFUNC_PAUSE to pause the transfer

Reported By: Zdenek Pavlas
Bug: https://bugzilla.redhat.com/857875
write_abort_test.py: test returning -1 from write callback