fix #5409: backup: fix copy-before-write timeout

The type for the copy-before-write timeout in nanoseconds was wrong.
By being just uint32_t, a maximum of slightly over 4 seconds was
possible. Larger values would overflow and thus the 45 seconds set by
Proxmox's backup with fleecing, resulted in effectively 2 seconds
timeout for copy-before-write operations.

Reported-by: Friedrich Weber <f.weber@proxmox.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

debian/patches/series

@@ -2,6 +2,7 @@ extra/0001-monitor-qmp-fix-race-with-clients-disconnecting-earl.patch
 extra/0002-scsi-megasas-Internal-cdbs-have-16-byte-length.patch
 extra/0003-ide-avoid-potential-deadlock-when-draining-during-tr.patch
 extra/0004-Revert-x86-acpi-workaround-Windows-not-handling-name.patch
+extra/0005-block-copy-before-write-use-uint64_t-for-timeout-in-.patch
 bitmap-mirror/0001-drive-mirror-add-support-for-sync-bitmap-mode-never.patch
 bitmap-mirror/0002-drive-mirror-add-support-for-conditional-and-always-.patch
 bitmap-mirror/0003-mirror-add-check-for-bitmap-mode-without-bitmap.patch