Motivation:
The nfs spec requires, that after restart client presents the same
client id. Though this is not that important for the test client,
however, makes testing more reliable.

Modification:
generate client is string to be

java class name + user + host name.

for example: org.dcache.nfs.v4.client.Main: tigran on nairi

Result:
server friendly test client.

Acked-by: Paul Millar
Acked-by: Lea Morschel
Target: master