NPE if provisioning requisition name has spaces

If you create a provisioning requisition with a space in the name, updates will fail with a NPE. The error at the top of the stacktrace shows it choking on the spaces:

2016-02-13 00:20:51,663 WARN [Requisition-Accessor-Thread] o.o.n.p.p.RequisitionFileUtils: Trying to create snapshot for file:/opt/opennms/etc/imports/pending/SFO%20front%20end.xml, but /opt/opennms/etc/imports/pending/SFO%20front%20end.xml does not exist.