update themis_multibucket.spec to use themis client

Change-Id: I9c302dadb1045b3a99ac844dea41ff2e408cbfc5
Reviewed-on: http://review.couchbase.org/c/perfrunner/+/149229
Tested-by: Build Bot <[email protected]>
Reviewed-by: Korrigan Clark <[email protected]>

Author: bochun

clusters/themis_multibucket.spec

@@ -16,8 +16,7 @@ destination_bucket =
 
 [clients]
 hosts =
-    172.23.97.16
-    172.23.97.17
+    172.23.99.247
 credentials = root:couchbase
 
 [storage]