Use just sfdisk --json, --dump is not needed

src/disk_tool_utils.cpp

@@ -305,10 +305,10 @@ int write_zero(int fd, uint64_t offset, uint64_t size)
 json11::Json read_parttable(std::string dev)
 {
     std::string part_dump;
-    int r = shell_exec({ "sfdisk", "--dump", dev, "--json" }, "", &part_dump, NULL);
+    int r = shell_exec({ "sfdisk", "--json", dev }, "", &part_dump, NULL);
     if (r == 255)
     {
-        fprintf(stderr, "Error running sfdisk --dump %s --json\n", dev.c_str());
+        fprintf(stderr, "Error running sfdisk --json %s\n", dev.c_str());
         return json11::Json(false);
     }
     // Decode partition table
@@ -319,7 +319,7 @@ json11::Json read_parttable(std::string dev)
         pt = json11::Json::parse(part_dump, err);
         if (err != "")
         {
-            fprintf(stderr, "sfdisk --dump %s --json returned bad JSON: %s\n", dev.c_str(), part_dump.c_str());
+            fprintf(stderr, "sfdisk --json %s returned bad JSON: %s\n", dev.c_str(), part_dump.c_str());
             return json11::Json(false);
         }
         pt = pt["partitiontable"];