NFS Automount clients send mount requests to the server every 45 seconds

Issue

Constant mount/unmount activity, as seen in /var/log/messages:

Mar 28 10:40:11 ed mountd[6404]: authenticated unmount request from pc06:824 for /cm/cots (/cm/cots)
Mar 28 10:40:11 ed mountd[6404]: authenticated unmount request from pc06:827 for /work/spr_peer (/work/spr_peer)
Mar 28 10:40:14 ed mountd[6404]: authenticated mount request from pc06:836 for /work/spr_peer (/work/spr_peer)
Mar 28 10:40:42 ed mountd[6404]: authenticated mount request from pc06:925 for /cm/cots (/cm/cots)
Mar 28 10:41:11 ed mountd[6404]: authenticated unmount request from pc06:824 for /cm/cots (/cm/cots)