NetLoop initialization bug

The patch fixes the bug of partial initialization of global network
parameters.

Upon u-boot's start up the first ping command causes a failure of the
consequent TFTP command. It happens in the recently added mechanism of
the NetLoop initialization where initialization of global network
parameters is separated in the NetInitLoop routine which is called per
env_id change. Thus, ping request will initialize the network parameters
necessary for ping operation only, afterwards the env_changed_id will be
set to the env_id that will prevent all following initialization requests
from other protocols.
The problem is that the initialized by ping subset of network parameters
is not sufficient for other protocols and particularly for TFTP which
requires the NetServerIp also.

Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>