Previously, krata runtime allowed a single permit when performing operations.
This was necessary because the only IP allocation storage was xenstore, and
the commit of xenstore data happens after allocation. This commit introduces
IpVendor, a service which vends IPv4 and IPv6 addresses to guests using a
linear address strategy within an IP network space. The IpVendor table is
initialized from xenstore, and from there on out, the in-memory table
is the source of truth. This implementation is not perfect, but it will allow
us to lift the single permit limit, allowing guests to start concurrently.
