give the interface time to settle before rejoining mdns

[mobileoverlord]

While using nerves_init_gadget with wlan0 I have found that the multicast group memberships were not being established once the ip changes.

What I was experiencing
Once the device was fully booted and has connected to the network and the IP address is up mdns would not properly restart. I would no longer see mdns logger outpus in the console of the device, and I was no longer able to send queries to it from other devices on the network.
Here is the output of ``

Idx     Device    : Count Querier       Group    Users Timer    Reporter
1       lo        :     1      V3
                                010000E0     1 0:00000000               0
4       wlan0     :     1      V3
                                010000E0     1 0:00000000               0

What should happen
After adding in a sleep of 100 ms I was able to get consistent registration results. Here is the output of `` after

cmd("cat /proc/net/igmp")
Idx     Device    : Count Querier       Group    Users Timer    Reporter
1       lo        :     1      V3
                                010000E0     1 0:00000000               0
4       wlan0     :     3      V3
                                FB0000E0     1 0:00000000               0
                                010000E0     1 0:00000000               0

There is a deeper problem that is at play here and we need to revisit this to find a better solution. We need to come up with a way that we can monitor multicast group registrations

[fhunleth]

Merged. Sigh.