erasure-code: OSDMonitor::crush_ruleset_create_erasure needs ruleset

When OSDMonitor::crush_ruleset_create_erasure checks the ruleset for
existence, it must convert the ruleid into a ruleset before assigning it
back to the *ruleset parameter.

http://tracker.ceph.com/issues/9044 Fixes: #9044

Signed-off-by: Loic Dachary <loic@dachary.org>
erasure-code: ErasureCodeJerasure::create_ruleset must return a ruleset

CrushWrapper::add_simple_ruleset does not return a ruleset, it returns
a ruleid that must be converted into a ruleset before being returned.

http://tracker.ceph.com/issues/9044 Fixes: #9044

Signed-off-by: Loic Dachary <loic@dachary.org>
erasure-code: ErasureCodeIsa::create_ruleset must return a ruleset

http://tracker.ceph.com/issues/9044 Refs: #9044

Signed-off-by: Loic Dachary <loic@dachary.org>
osd: improve ruleno/ruleset consistency

rename variables to reflect when they hold a ruleset and when they hold
a rule id / ruleno in the hope to avoid bugs in the future.

Signed-off-by: Loic Dachary <loic@dachary.org>