networks: Simplifies spawnForkDNS to not get cluster server list
networks: Simplifies spawnForkDNS to not get cluster server list

Also changes this function to be called synchronously as it no longer depends on cluster status.

Also removes command line arguments for server leases.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

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