Remove unused task from manager create_volume flow

ExtractSchedulerSpecTask hasn't been ever used in the
create_volume flow, so it should be deleted.

Change-Id: Ia841e224bc253c68ed21520951016a1a90634faf
Merge "Remove unused task from manager create_volume flow"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f