Wrong endpoint paths in swagger files

[ma1112]

Description

Endpoints for the kernel interrupt and kernel restart endpoints miss the "/api" prefix that all other endpoints have in these files.
As a result when one auto-generates code from the swagger files, the functionalities that call these endpoints will not work.

Reproduce

One can already see that the endpoints need the /api prefix by e.g. creating a kernel with

POST /api/kernels

capturing the returned session ID and then calling the following endpoints. The first two work, the last two does not work.

POST /api/kernels<kernel_id>/interrupt
POST /api/kernels<kernel_id>/restart

POST /kernels<kernel_id>/interrupt
POST /kernels<kernel_id>/interrupt

Expected behavior

swagger files should have the proper api path

Context

See also this issue that reports different defects in the swagger files. #404