net: Disable namespace compatibility support for tests

Do not enable network compatibility mode flag for network tests
so that we will get better coverage of the wrong network APIs
used.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>
diff --git a/subsys/net/ip/Kconfig b/subsys/net/ip/Kconfig
index 11eb35f..c903d95 100644
--- a/subsys/net/ip/Kconfig
+++ b/subsys/net/ip/Kconfig
@@ -10,6 +10,9 @@
 
 config NET_NAMESPACE_COMPAT_MODE
 	bool "Network namespace compatibility mode"
+	# Disable the compatibility mode for network tests. But if the tests
+	# uses POSIX APIs, then currently the compat mode is needed.
+	depends on !NET_TEST || POSIX_API
 	default y
 	help
 	  The networking APIs and code is now namespaced i.e., relevant network