tests: do not include <errno.h> unnecessarily

tests: do not include <errno.h> unnecessarily

Automatically change tests/*.c files using the following script:

for f in tests/*.c; do
	grep -Fv errno.h "$f" |
	grep -Ewq '(si_)?errno|SOCK_FILTER_DENY_SYSCALL' ||
		sed -i '/# *include *<errno\.h>/d' "$f"
done