add gethostid() testcase

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

test/inet/gethostid.c

@@ -0,0 +1,6 @@
+#include <unistd.h>
+#include <stdio.h>
+int main(void) {
+	printf("hostid=%d\n", gethostid());
+	return 0;
+}