OpenApi: Remove incorrect list POST requests

OpenApi: Remove incorrect list POST requests

Our logic creates POST requests for lists with keys, containing
multiple resources in payload. This does not align with the expected
structure for creating child resources in the YANG model.

Added condition that prevents the creation of POST requests
that has list as a last element.

JIRA: NETCONF-1101
Change-Id: I46820f222c9c5ef8078ac8675d2adc12b06f1253
Signed-off-by: Yaroslav Lastivka <yaroslav.lastivka@pantheon.tech>
Signed-off-by: Ivan Hrasko <ivan.hrasko@pantheon.tech>
Signed-off-by: Samuel Schneider <samuel.schneider@pantheon.tech>
(cherry picked from commit 1d64392feb896e9c74f4d9085eea52bbfdac1211)