libmount: propagate first error of multiple filesystem types

libmount: propagate first error of multiple filesystem types

Use the same error handling logic as do_mount_by_pattern() to better
handle the case where EROFS is returned from the first filesystem in a
list but subsequent filesystems overwrite this status with, for example,
ENODEV.

This allows read-only devices to mount without the user needing to
explicitly specify "ro" while specifying a list of potential
filesystems, some of which may not be available.

Signed-off-by: John Keeping <jkeeping@inmusicbrands.com>