Bug 8837: Dewey cn_sort inaccurate

Bug 8837: Dewey cn_sort inaccurate

This patch fix the cn_sort sorting accurace described by Joy Nelson.

Testing:

I) Appy the bug 12424 patch

Before applying this patch:
0) Select 3 items.
1) Edit the items selected
2) Change "Full call number" option to 971/P23w/v.1-2/pt.8, 971.01/P23w/v.1-2/pt.6-7 and 971.01/P23w/v.1-2/pt.7
3) Save changes
4) Valide 971P23WV_12PT_8_000000000000000, 971_000000000000000_01P23WV_12PT_67 and 971_01P23WV_12PT_700000000000000  (table items - cn_sort column).

After applying this patch:
5) Edit again the item selected in 0
3) Save changes
4) Valide 971_000000000000000_P23W_V_12_PT_8, 971_010000000000000_P23W_V_12_PT_67, 971_010000000000000_P23W_V_12_PT_7 (table items - cn_sort column).

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>