fs_mgr: fs_mgr_rm_all error propagation inconsequential EPERM

If in fs_mgr_rm_all opendir on a subdirectory fails because of EPERM,
but a subsequent rmdir succeeds then there was no reason to report
the EPERM as an overall failure error code.

Test: manual
Bug: 117605276
Change-Id: I79fbf8567af1667094595e59ca2b536450f34b94
1 file changed