Update randstream to 0.5.0

[glehmann]

This version adds progress report even when the standard error is not a tty, which is convenient when working with large volumes.

This PR is part of a stack containing 18 PRs:

1. master
2. storage: avoid removing the xva/vdi before going in the debugger #436
3. storage: test large volumes #437
4. host: include mdadm RAID devices in disk detection #447
5. "Update randstream to 0.5.0" (this PR)
6. storage: Avoid writing the whole device in coalesce tests #449
7. storage: avoid writing the whole device in migration tests #450
8. xva/vdi: only write a small data amount in large volumes for faster tests #452
9. storage: test full device write #453
10. storage: test that we can't create a vdi over its max allowed size #454
11. storage: add jobs for large volume tests #461
12. skip large volume tests for zvol and nfsv4 #464
13. storage: add comprehensive tests for lvmohba storage repositories #470
14. storage: free space for XVA import by destroying source VM first #471
15. storage: limit data written per VDI with --write-volume-cap #481
16. migration: create a xfs sr on the second host for intra/cross-pool migration #497
17. Enhance block device management #498
18. Add VHD_MAX and QCOW2_MAX symbolic size constants #500
19. partially_populate_device: align spans to block size for better performance #509