Adding rshared to fstab causes error meesages in rc.log

[drwheeler]

To make a mount shared #526 adds some code in init.d/root

Adding rshared to the mount options in fstab works, but only if rshared is not the last option
rw,rshared,relatime works
rw,relatime,rshared does not work : the code looks for ,rshared, not ,rshared

• Making root filesystem shared [ ok ]

After that init.d/root remounts all filesystems and when it gets to one with a ,rshared, option, mount complains because rshared is not a known option

• Remounting filesystems ...
  mount: mounting /dev/sda3 on / failed: Invalid argument [ ok ]