Bug 16806: no error message for 'too_soon' renewal

Bug 16806: no error message for 'too_soon' renewal

To test:
-  for a particular item type & patron category, configure a non-zero
"no renewal before" date so items can't be immediately renewed
- sign in as a patron in aforementioned patron category
- check out an item of aforementioned item type
- go to your renewals page in OPAC /cgi-bin/koha/opac-user.pl
- an error messages appears in the div.alert.dialog up top

Sponsored-by: California College of the Arts
Signed-off-by: Brendon Ford <brendon.ford@manhattan.edu>
Signed-off-by: Irma Birchall <irma@calyx.net.au>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>