core: swap priority can be negative

Negative priorities are useful for swap targets which should be only used as
last resort.

src/shared/fstab-util.c

@@ -186,8 +186,7 @@ int fstab_extract_values(const char *opts, const char *name, char ***values) {
 
 int fstab_find_pri(const char *options, int *ret) {
         _cleanup_free_ char *opt = NULL;
-        int r;
-        unsigned pri;
+        int r, pri;
 
         assert(ret);
 
@@ -197,14 +196,11 @@ int fstab_find_pri(const char *options, int *ret) {
         if (r == 0 || !opt)
                 return 0;
 
-        r = safe_atou(opt, &pri);
+        r = safe_atoi(opt, &pri);
         if (r < 0)
                 return r;
 
-        if ((int) pri < 0)
-                return -ERANGE;
-
-        *ret = (int) pri;
+        *ret = pri;
         return 1;
 }