Do not mount LV by UUID from fstab.

I should not reference LV in fstab by UUID, because if i have snapshot of this
LV, it is unknown which one (origin or snapshot) will be mounted.

xargs, arguments separator and escapes.

xargs uses blanks (not only newlines!) to split input line into arguments.
Though, there is some options, which turns this defailt off implicitly or
explicitly.

Here is summary:

    +--------+--------------------+---------------------+
    | Option | Argument separator | Escapes             |
    +--------+--------------------+---------------------+
    | -L     | blank              | Interpreted (work)  |
    +--------+--------------------+---------------------+
    | -d     | user defined       | Literal (not work)  | 
    +--------+--------------------+---------------------+
    | -I     | newline            | Interpreted (work)  |
    +--------+--------------------+---------------------+