crimson: bump seastore_max_concurrent_transactions size from 8->128, clarify description

Retain old value for qa coverage.

Signed-off-by: Samuel Just <[email protected]>
(cherry picked from commit 988c668)

Author: athanatos

qa/config/crimson_qa_overrides.yaml

@@ -11,6 +11,7 @@ overrides:
         crimson osd obc lru size: 10
         debug ms: 20
         seastore cache lru size: 64M
+        seastore max concurrent transactions: 8
     flavor: crimson
   workunit:
     env:

src/common/options/crimson.yaml.in

@@ -162,8 +162,8 @@ options:
 - name: seastore_max_concurrent_transactions
   type: uint
   level: advanced
-  desc: maximum concurrent transactions that seastore allows
-  default: 8
+  desc: maximum concurrent transactions that seastore allows (per reactor)
+  default: 128
 - name: seastore_main_device_type
   type: str
   level: dev