+++ This bug was initially created as a clone of Bug #620837 +++ Clone of a corresponding bug fixed in RHEL-6... This bug was found by examination of the source. During freeing of the data structure used to hold the definition for host bridge interfaces (those created via the iface-define command), a free of the delay string was inadvertently omitted.
Note that currently there are no plans to support host interface configuration (virInterface*, virsh iface-*) in RHEL5, as it requires the netcf library, and netcf requires a version of libnl that is ABI-incompatible with the libnl used in RHEL5. So although having this fix in the RHEL5 version of libvirt source is a good idea just for completeness' sake, it will not have any material affect.
Ah, right I somehow overlooked this bug fixed a feature which is disabled in the spec file. There's no need to carry one more patch with no effect. Let's just drop it.