qemu: blockCopy: Pass adjusted bandwidth when called via blockRebase

The block copy API takes the speed in bytes/s rather than MiB/s that was
the prior approach in virDomainBlockRebase. We correctly converted the
speed to bytes/s in the old API but we still called the common helper
virDomainBlockCopyCommon with the unadjusted variable.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1207122
(cherry picked from commit 3c6a72d5)

src/qemu/qemu_driver.c

@@ -16334,7 +16334,7 @@ qemuDomainBlockRebase(virDomainPtr dom, const char *path, const char *base,
     flags &= (VIR_DOMAIN_BLOCK_REBASE_SHALLOW |
               VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT);
     ret = qemuDomainBlockCopyCommon(vm, dom->conn, path, dest,
-                                    bandwidth, 0, 0, flags, true);
+                                    speed, 0, 0, flags, true);
     dest = NULL;
 
  cleanup: