Description of problem:

Earlier versions of Fedora honored the interface-mtu setting.
Fedora 20 does not.
This is critical for networks where the default MTU does not work and DHCP tells the client what MTU top use.
Note that this worked in previous versions of Fedora, so this is a regression in F20.

Version-Release number of selected component (if applicable):

NetworkManager-0.9.9.0-22.git20131003.fc20.x86_64
dhcp-common-4.2.5-26.fc20.x86_64
dhcp-libs-4.2.5-26.fc20.x86_64
dhclient-4.2.5-26.fc20.x86_64

How reproducible:
100%


Steps to Reproduce:
1. Issue an interface-mtu option in a DHCP configuration
2. Start a F20 DHCP client connection against that config
3. Notice that the dhcp lease in /var/lib/NetworkManager... contains the correct interface-mtu setting from the DHCP config
4. Notice that "ifconfig" shows the default MTU, not the setting from the dhcp lease

Actual results:
The interface sets the default MTU, ignoring the dhcp setting.
In my case this causes all TCP traffic to fail because the default MTU is too big for the network

Expected results:

the DHCP client should honor the interface-mtu setting like it did in previous versions of Fedora.

Additional info:

The lease info in /var/lib/... contains:

lease {
  interface "ens32";
   ...
  option interface-mtu 1476;
   ...
}

But ifconfig has an MTU of 1500.