block: iscsi build fix if LIBISCSI_FEATURE_IOVECTOR is not defined

Commit b03c3805 introduced the function
iscsi_allocationmap_is_allocated(), however it is only used within a
code block that is conditionally compiled.  This produces a warning
(error with -werror) of "defined but not used" for the the function, if
LIBISCSI_FEATURE_IOVECTOR is not defined.

This wraps iscsi_allocationmap_is_allocated() in the same conditional.
Signed-off-by: NJeff Cody <jcody@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

block/iscsi.c

@@ -381,6 +381,7 @@ retry:
 }
 
 
+#if defined(LIBISCSI_FEATURE_IOVECTOR)
 static bool iscsi_allocationmap_is_allocated(IscsiLun *iscsilun,
                                              int64_t sector_num, int nb_sectors)
 {
@@ -393,9 +394,6 @@ static bool iscsi_allocationmap_is_allocated(IscsiLun *iscsilun,
                            sector_num / iscsilun->cluster_sectors) == size);
 }
 
-
-#if defined(LIBISCSI_FEATURE_IOVECTOR)
-
 static int64_t coroutine_fn iscsi_co_get_block_status(BlockDriverState *bs,
                                                   int64_t sector_num,
                                                   int nb_sectors, int *pnum)