network-manager: add network-pre dependencies

In I3d379d35e7b000f32c3f6cc197c8aaafebc683fb we found that just having
network-pre.target was not sufficient to get the interfaces to come
up, and found emperically using local-fs.target made things work in CI
and on our hosts [1].  However, it always seemed to be a race
condition; the same .qcow2 run in another cloud environment would
reliably configure its interfaces in one provider but not another.

However, we now have yet antoher new cloud environment where we are
still seeing races between updating the config files and starting
NetworkManager.  It seems clear now that we also need to add
dependencies on network-pre.target

The key learning here might be that we required the
After=local-fs.target all along, to make sure we could write the files
to disk, but we should have kept the network-pre dependencies.  So
restore these values.

[1] https://review.opendev.org/#/c/618964/9..17/glean/init/glean-nm%2540.service

Depends-On: https://review.opendev.org/670102
Change-Id: Ib650d4c4303535205a62600e2c8657eae45dc4a4

glean/init/glean-nm@.service

@@ -1,6 +1,7 @@
 [Unit]
 Description=Glean for interface %I with NetworkManager
-Wants=local-fs.target
+Before=network-pre.target
+Wants=network-pre.target
 After=local-fs.target
 
 # Red Hat