Replacing fs_mgr_dir_is_writable(work) with fs_mgr_rw_access(work) to

check whether the scratch partition is writable.

Delate fs_mgr_dir_is_writable, as it may cause remount to fail.

Steps to reproduce:
1.adb root
2.adb remount
3.adb reboot
4.adb remount
5.push files to the system partition until the scratch partition is full
6.check that the Available of /mnt/scratch is zero through the df command
7.reboot
8.adb root
9.adb remount
Now, overlayfs failed to mount.

But I want to continue to view the files that were previously pushed to
the system partition.
Mounting of overlayfs should not be blocked when there is not enough space.
It seems reasonable to use fs_mgr_rw_access(work) to check whether
the partition is writable.
We should allow mount even if scratch is full, because this allows
the user to delete previously pushed files to free up space.

Bug: 240635368
Change-Id: I726ccd064cfabfab29789e7c690ea8cb574a6344
Signed-off-by: yi.sun <yi.sun@unisoc.com>