Clean up array insertion to skip unnecessary memmove

Clean up array insertion to skip unnecessary memmove

The previous elements need to be moved only if we are inserting the new
network in the middle of the list. While the memmove of zero bytes at
the end of the array does not cause real problems, some static analyzers
complain about this, so in addition to slightly optimized
implementation, this removes some analyzer warnings, too.

Signed-hostap: Jouni Malinen <j@w1.fi>