net: app: Fix compilation if TCP is not enabled
net: app: Fix compilation if TCP is not enabled

If building a server that does not support TCP, then the
get_server_ctx() is not needed and thus needs to be compiled out.

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

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