systemd: ignore hw timestamps in containers

They are irrelevant and misleading.

E.g. systemd-analyze:

  Startup finished in 6d 4h 15min 32.330s (kernel) + 49ms 914us (userspace) = 6d 4h 15min 32.380s

becomes

Startup finished in 53.735ms (userspace) = 53.735ms

which looks much better :)

src/shared/virt.c

@@ -168,7 +168,7 @@ int detect_vm(const char **id) {
 }
 
 int detect_container(const char **id) {
-        char *e = NULL;
+        char _cleanup_free_ *e = NULL;
         int r;
 
         /* Unfortunately many of these operations require root access
@@ -216,8 +216,6 @@ int detect_container(const char **id) {
                         *id = "other";
         }
 
-        free(e);
-
         return r;
 }