Update git submodules

* Update docs/submodules/so.git from branch 'master'
  to 21e51ae1290ac58d9f579333199098f98615f5b2
  - Merge "Missing VNF Recipe for Optical service"
  - Missing VNF Recipe for Optical service
    
    Added missing Recipe for orchestration of OTN services in Optical domain
    
    Change-Id: I515448ca6c799fbcaddbbe10fe803e47308cd8fe
    Issue-ID: SO-2773
    Signed-off-by: Srinivasan Ramanathan <srinivasan.ramanathan2@us.fujitsu.com>
    
1 file changed