Makefile: fix test selection for privileged tests
Makefile: fix test selection for privileged tests

Because of a small mistake in the Makefile ("$(pkg)" to evaluate the
variable with make, when it is a shell variable and should really be
"$$pkg"), passing TESTPKGS=pkg/foo/bar when running "make
test-privileged" does not behave as expected and runs all test instead.
Indeed, the shell command does not pass anything to xargs, and the grep
is done recursively with no directory argument, so it applies to the
entire cilium repository. Let's fix it.

This commit log contains 296 times the number of characters that are
changed in the patch.

Signed-off-by: Quentin Monnet <d6b8e48afb2534b213e391cab43016505747a234@isovalent.com>

tgraf/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,cilium-team/cilium,michi-covalent/cilium,tklauser/cilium,cilium-team/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium