runtime: Implement mount option filtering

[r10r]

liblxc fails to mount filesystems if unsupported mount options are passed to lxc.mount.entry.
It does however support the option optional to continue with container startup even if a mountpoint fails.
See man lxc.container.conf

crio-lxc should support filtering of mount options, to handle unsupported mount options gracefully.

[r10r]

The mount system call does not support to ignore unsupported mount options.
The mount binary itself implements the option -s which is only partially implemented See man 8 mount

-s     Tolerate  sloppy  mount  options  rather  than  failing.  
 This will ignore mount options not supported by a filesystem type.  
Not all filesystems support this option.  
Currently it's supported by the  mount.nfs mount helper only.

Currently almost all mount options are passed through to liblxc.
But in certain configurations drachenfels-de/lxcri-defork#13 unsupported mount options are passed from crio-o.

[r10r]

containers/storage does check for supported mount options.
It simply calls mount with the options to check and if it fails the option is not supported.

[r10r]

Mount options are now filtered to ignore unsupported options, but that's not a final solution.

lxcri/mount.go

Line 31 in cbc79e1

func filterMountOptions(rt *Runtime, fs string, opts []string) []string {