init: Don't fail immediately if no network device found

This patch is following an error since on a real server.
The log error was looking like the following :

 ################################################################
 Starting networking
 ################################################################
 Creating SSH2 RSA key; this may take some time ...
 Creating SSH2 DSA key; this may take some time ...
 Creating SSH2 ECDSA key; this may take some time ...unknown key type ecdsa
 Enabling Ethernet Links
 Waiting a few seconds to catch network link
 List of available network devices is :
 Required kernel modules for 2.6.32-431.17.1.el6.x86_64 x86_64 are : ehci_hcd, megaraid_sas, pcieport,
 15:00.0 0200: 14e4:165f
 15:00.1 0200: 14e4:165f
 16:00.0 0200: 14e4:165f
 16:00.1 0200: 14e4:165f
 15:00.0 0200: 14e4:165f
 15:00.1 0200: 14e4:165f
 16:00.0 0200: 14e4:165f
 16:00.1 0200: 14e4:165f
 15:00.0 0200: 14e4:165f
 15:00.1 0200: 14e4:165f
 16:00.0 0200: 14e4:165f
 16:00.1 0200: 14e4:165f
 15:00.0 0200: 14e4:165f
 15:00.1 0200: 14e4:165f
 16:00.0 0200: 14e4:165f
 16:00.1 0200: 14e4:165f
 No Network interface found !

If no network interface got found, we shall make another try before
being fatal. Maybe we could have a slight delay between the probing and
the actual entry.

This patch is so making a couple of retry before being fatal.