VPN is broken in Xenial

[Ovidiu-Florin BOGDAN]

[Impact]
The new Network manager has some extra options and this breaks the usage of (probably) any type of VPN. No new connection can be created or existing ones edited.

It fails with the message: «connection.gateway-ping-timeout: can not set property: value "18454592" of type 'guint' is invalid or out of range for property 'gateway-ping-timeout' of type 'guint'»

[Testcase]
Before patch:
  * Install Kubuntu 16.04
  * Connect to a network (connection being done automatically)
  * Create a new VPN connection
    * For example PPTP
    * Type in gateway any string longer than one character
    * Click ok
    * Receive notification error «connection.gateway-ping-timeout: can not set property: value "18454592" of type 'guint' is invalid or out of range for property 'gateway-ping-timeout' of type 'guint'»
    * notice connection is not created
  * Create a new connection (wireless or wired)
    * Change the IP to manual
    * Save
    * Receive noification error «same as above»
    * Notice connection is not created
  * Import a VPN connection
    * Save
    * Receive notification error «same as above»
    * Notice connection is not created

After the patch:
    Do all of the above, and the connection gets created every time. Test each connection and they work.

[Fix]
In KDE bug https://bugs.kde.org/show_bug.cgi?id=362141 for this issue a fix is commited. This is released in KDE Frameworks 5.21. The patch can be cherry picked and applied to networkmanager-qt 5.18.

[Ovidiu-Florin BOGDAN (ovidiu-florin)]

Here is the commit diff that solves the issue: https://quickgit.kde.org/?p=networkmanager-qt.git&a=commitdiff&h=93faf9ec94826c5d753aa090313472800ee41b86

[Ovidiu-Florin BOGDAN (ovidiu-florin)]

@clivejo has set up a patch available here: https://launchpad.net/~clivejo/+archive/ubuntu/xenial

I've tested the patch and this solves the issue. So far I don't see any regressions.