tests: use AM_CFLAGS instead of CFLAGS directly

Signed-off-by: Thomas Graf <tgraf@suug.ch>
socket: Warn via debug message if local port namespace is exhausted

Signed-off-by: Thomas Graf <tgraf@suug.ch>
cache: Return -NLE_PROTO_MISMATCH if socket provided mismatches cache protocol

Signed-off-by: Thomas Graf <tgraf@suug.ch>