Bug 17392 - opac/svc/overdrive_proxy is not plack safe

Bug 17392 - opac/svc/overdrive_proxy is not plack safe

This patch simply replaces the ';'  in the param passed to OverDrive
with '&'

To test:
1 - Enable overdrive (requires an account)
2 - Perform an opac search
3 - Note the number of overdrive results reported
4 - Click the link to view the actual overdrive results
5 - Note the result numbers don't match
6 - Apply patch
7 - Repeat 1-4 and note results numbers match and results are relevant
8 - Test a search with a ';' to ensure this patch isn't breaking
searches

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Katrin Fischer  <katrin.fischer@bsz-bw.de>
Verified by reading code - couldn't verify using Overdrive.

Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>