OpenAPI: Do not hardcode action path

Action paths are created in BaseYangOpenApiGenerator by appending rests/operations instead of rests/data. Both sides of this replacing are not configurable. If user (for example lighty.io) uses custom OpenAPI path this can lead to troubles as seen in NETCONF-860.

Hardcoded expected behaviour: rests/data<THE-REST-OF-PATH> -> rests/operations<THE-REST-OF-PATH>

Unexpected hardcoded behaviour: restconf/data<THE-REST-OF-PATH> -> rest/operationsata<THE-REST-OF-PATH>