Print dialog polls printserver for printers several times per second

[Alex Korobkin]

How to reproduce:
1. Enable debugging in CUPS by sudo cupsctl --debug-logging
2. Open a GTK+ application and press Ctrl+P to show Print dialog (for example, evince or eog).
3. Notice that CUPS is polled two or three times per second for printer list:
grep CUPS-Get-Printers /var/log/cups/error_log

Tested on Ubuntu 12.04 x64 with libgtk-3-0 3.4.2, eog 3.4.2, evince 3.4.0, Ubuntu 14.04 x64 with libgtk-3-0 3.10.8.

If you open three apps and press Ctrl+P in each, printserver will be polled three times more frequently.

This behavior puts unnecessary strain on printservers, especially if they serve hundreds or thousands of clients in enterprise environment.

Is there a way to adjust this polling interval?

Excerpt from CUPS error_log:
D [04/Nov/2013:17:57:21 -0500] cupsdReadClient: 13 1.1 CUPS-Get-Printers 1
D [04/Nov/2013:17:57:21 -0500] Returning IPP successful-ok for CUPS-Get-Printers (no URI) from localhost
D [04/Nov/2013:17:57:21 -0500] cupsdReadClient: 13 1.1 CUPS-Get-Printers 1
D [04/Nov/2013:17:57:21 -0500] Returning IPP successful-ok for CUPS-Get-Printers (no URI) from localhost
D [04/Nov/2013:17:57:21 -0500] cupsdReadClient: 13 1.1 CUPS-Get-Printers 1
D [04/Nov/2013:17:57:21 -0500] Returning IPP successful-ok for CUPS-Get-Printers (no URI) from localhost
D [04/Nov/2013:17:57:22 -0500] cupsdReadClient: 13 1.1 CUPS-Get-Printers 1