Merge PR #21033 into wip-sage-testing-20180407.022623

* refs/pull/21033/head:
	buffer: kill push_front
	tools/RadosDump: avoid bufferlist::push_front
	os/filestore/FileJournal: avoid push_front
	erasure-code: avoid bufferlist::push_front
	buffer: kill claim_prepend
	unittest_compression: avoid claim_prepend
	os/bluestore: avoid claim_prepend
	osdc/Striper: rewrite assemble_result without push_front or claim_prepend

Reviewed-by: Radoslaw Zarzynski <rzarzyns@redhat.com>
Reviewed-by: Jesse Williamson <jwilliamson@suse.de>