Qubes-specific options must be added in NetworkManager.conf, even if
those lines are commented out by default. The problem is solved by using
extended regular expressions.
Apparently unmanaged devices are loaded only from main
NetworkManager.conf. Exactly the same line pasted (not typed!) to main
NetworkManager.conf works, but in
/etc/NetworkManager/conf.d/30-qubes.conf it doesn't.
BTW There was a typo in option name ("unmanaged_devices" instead of
"unmanaged-devices", but it wasn't the cause).
This reverts commit 6c4831339c.
QubesOS/qubes-issues#1176
Do not modify main /etc/NetworkManager/NetworkManager.conf as it would
cause conflicts during updates. Use
/etc/NetworkManager/conf.d/30-qubes.conf instead.
Also remove some dead code for dynamically generated parts (no longer
required to "blacklist" eth0 in VMs - we have proper connection
generated for it). It was commented out for some time already
FixesQubesOS/qubes-issues#1176
In FC15, NetworkManager by default uses global connections ("Available to all users"). Save them in /rw instead of /etc, to preserve them across reboots.