* src/utils/mount.ecryptfs_private.c: Implement proper option parsing to restore the -f option when unmounting and display a helpful usage message (LP: #1454388) * src/utils/mount.ecryptfs_private.c: Add an option, -d, to umount.ecryptfs_private to treat the situation where the encrypted private session counter is nonzero, after decrementing it, as a non-error situation. No error message is printed to stderr and the exit status is 0. * src/pam_ecryptfs/pam_ecryptfs.c: Use the new umount.ecryptfs_private '-d' option to silence the error message that was printed to stderr when the encrypted private session counter is nonzero after being decremented. (LP: #1454319) * src/utils/ecryptfs-umount-private: Return 1 if umount.ecryptfs_private encounters an error. The ecryptfs-umount-private script was previously returning 0 even when umount.ecryptfs_private exited upon error.