fs_mgr_overlayfs: Don't try to mount scratch if already mounted

This eliminates spammy logs.

Bug: 306124139
Test: adb remount -v && check the output logs
Change-Id: I3143f5865b5292ba581009179c7e7141afa8fda5
diff --git a/fs_mgr/fs_mgr_overlayfs_mount.cpp b/fs_mgr/fs_mgr_overlayfs_mount.cpp
index 0dadbff..66faecd 100644
--- a/fs_mgr/fs_mgr_overlayfs_mount.cpp
+++ b/fs_mgr/fs_mgr_overlayfs_mount.cpp
@@ -707,7 +707,7 @@
         return false;
     }
     auto ret = true;
-    auto scratch_can_be_mounted = true;
+    auto scratch_can_be_mounted = !fs_mgr_overlayfs_already_mounted(kScratchMountPoint, false);
     for (const auto& entry : fs_mgr_overlayfs_candidate_list(*fstab)) {
         if (fs_mgr_is_verity_enabled(entry)) continue;
         auto mount_point = fs_mgr_mount_point(entry.mount_point);