crimson/osd/recovery_backend: scan_for_backfill pass start by value

See: https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rcoro-reference-parameters

Signed-off-by: Matan Breizman <[email protected]>

Author: Matan-B

src/crimson/osd/recovery_backend.cc

@@ -222,7 +222,7 @@ RecoveryBackend::handle_backfill_remove(
 
 RecoveryBackend::interruptible_future<BackfillInterval>
 RecoveryBackend::scan_for_backfill(
-  const hobject_t& start,
+  const hobject_t start,
   [[maybe_unused]] const std::int64_t min,
   const std::int64_t max)
 {

src/crimson/osd/recovery_backend.h

@@ -90,7 +90,7 @@ class RecoveryBackend {
     eversion_t need) = 0;
 
   interruptible_future<BackfillInterval> scan_for_backfill(
-    const hobject_t& from,
+    const hobject_t from,
     std::int64_t min,
     std::int64_t max);