Fix return values from jemalloc hooks

For OS provider, merge, split and commits are nops.
This means we should return false, not true from
those hooks.

Ref: https://github.com/memkind/memkind/blob/c425635feb0367c43da8fa0deadb50a4bc127988/src/memkind_arena.c

Author: igchor

src/pool/pool_jemalloc.c

@@ -136,7 +136,7 @@ static bool arena_extent_commit(extent_hooks_t *extent_hooks, void *addr,
     (void)length;       // unused
     (void)arena_ind;    // unused
 
-    return true; // true means failure (unsupported)
+    return false; // false means success (commit is a nop)
 }
 
 // arena_extent_decommit - an extent decommit function conforms to the extent_decommit_t type
@@ -215,7 +215,7 @@ static bool arena_extent_split(extent_hooks_t *extent_hooks, void *addr,
     (void)committed;    // unused
     (void)arena_ind;    // unused
 
-    return true; // true means failure (unsupported)
+    return false; // false means success (split is a nop)
 }
 
 // arena_extent_merge - an extent merge function conforms to the extent_merge_t type and optionally
@@ -235,7 +235,7 @@ static bool arena_extent_merge(extent_hooks_t *extent_hooks, void *addr_a,
     (void)committed;    // unused
     (void)arena_ind;    // unused
 
-    return true; // true means failure (unsupported)
+    return false; // false means success (merge is a nop)
 }
 
 // The extent_hooks_t structure comprises function pointers which are described individually below.