logging_manager: Implement LoggingFile.isatty() for completeness, return False

yum-cli uses sys.stdout.isatty() in various places, so it will fail when
called from autotest since LoggingFile.isatty() does not exist.
Return False since LoggingFile is not emulating a tty.

Changes from v1:
   * Fixed spacing

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
logging_manager: Implement LoggingFile.writelines()

Existing code calls sys.stdout.writelines() because this method is
expected as part of the file object protocol.  When run in autotest
sys.stdout is actually a LoggingFile.  Implement writelines()
in LoggingFile to be more compliant with the File Object protocol.

Changes from v1:
 * Fixed docstring and removed unrelated comment

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>