Quote mount point when resizing jfs (#782681)

Attempting to grow an already mounted jfs where the mount point
contained spaces failed like this:

    Grow /dev/sdb2 from 1.00 GiB to 1.50 GiB
    + calibrate /dev/sdb2
    + grow partition from 1.00 GiB to 1.50 GiB
    + grow file system to fill the partition
      + mount -v -t jfs -o remount,resize /dev/sdb2 /tmp/File System Label
        Usage:
        mount [-lhV]
        mount -a [options]
        mount [options] [--source[ <source> | [--target] <directory>
        mount [options] <source> <directory>
        mount <operation> <mountpoint> [<target>]
        ...

Apply the rule to always enclose mount points within double quotes
within command lines.

Bug 782681 - btrfs partitions mounted with whitespace cannot be resized