6220 memleak in l2arc on debug build

*** 1299,1308 ****
--- 1299,1315 ----
                   * might try to be accessed, even though it was removed.
                   */
                  VERIFY(!HDR_L2_WRITING(hdr));
                  VERIFY3P(hdr->b_l1hdr.b_tmp_cdata, ==, NULL);
  
+ #ifdef ZFS_DEBUG
+                 if (hdr->b_l1hdr.b_thawed != NULL) {
+                         kmem_free(hdr->b_l1hdr.b_thawed, 1);
+                         hdr->b_l1hdr.b_thawed = NULL;
+                 }
+ #endif
+ 
                  nhdr->b_flags &= ~ARC_FLAG_HAS_L1HDR;
          }
          /*
           * The header has been reallocated so we need to re-insert it into any
           * lists it was on.