fix server group rebalance tests

Change-Id: I2399bc9a8c6a8ca94394f30ed066d44044f53fc6
Reviewed-on: https://review.couchbase.org/c/perfrunner/+/167146
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Bo-Chun Wang <bo-chun.wang@couchbase.com>

Author: bochun

tests/server_group/kv_reb_out_300M_6n_1g.test

@@ -18,7 +18,7 @@ kernel_mem_limit_services = kv
 eviction_policy = fullEviction
 
 [load]
-items = 150000000
+items = 300000000
 size = 1024
 workers = 80
 key_fmtr = hex
@@ -30,7 +30,7 @@ reads = 90
 updates = 10
 deletes = 0
 throughput = 15000
-items = 150000000
+items = 300000000
 workers = 40
 
 [rebalance]

tests/server_group/kv_reb_out_300M_6n_2g.test

@@ -18,7 +18,7 @@ kernel_mem_limit_services = kv
 eviction_policy = fullEviction
 
 [load]
-items = 150000000
+items = 300000000
 size = 1024
 workers = 80
 key_fmtr = hex
@@ -30,7 +30,7 @@ reads = 90
 updates = 10
 deletes = 0
 throughput = 15000
-items = 150000000
+items = 300000000
 workers = 40
 
 [rebalance]