mon/PGmap: Add warn description for bluestore fragmentation

Add a user friendly description for
BLUESTORE_FREE_FRAGMENTATION warning.  This is displayed
in `ceph -s` and `ceph health detail` to help the user
understand what BLUESTORE_FREE_FRAGMENTATION means.

Signed-off-by: Michael J. Kidd <[email protected]>

Author: linuxkidd

src/mon/PGMap.cc

@@ -3317,6 +3317,8 @@ void PGMap::get_health_checks(
 	for (auto str : asum.second.second) {
 	  summary += str;
 	}
+      } else if (asum.first == "BLUESTORE_FREE_FRAGMENTATION") {
+        summary += " experiencing high free space fragmentation of BlueStore";
       }
 
       auto& d = checks->add(asum.first, HEALTH_WARN, summary, asum.second.first);