[Canvas] /api/canvas/fns is executed on opening different apps (home, discover, dashboard, etc)

[dmlemeshko]

Kibana version: latest master

Elasticsearch version: latest snapshot

Server OS version: MacOS 11.4

Browser version: Chrome 92.0.4515.131

Browser OS version: MacOS 11.4

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug: /api/canvas/fns on opening different apps (home, discover, dashboard, etc)

Steps to reproduce:

1. Start Kibana
2. While logging in, check Dev Tools/Network tab for requests done on /app/home, go directly to http://localhost:5620/app/discover check requests again

Expected behavior: /api/canvas/fns should not be called on other plugins.

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

This is the API call sample that been run on other plugins:

curl 'http://localhost:5620/api/canvas/fns' \
  -H 'Connection: keep-alive' \
  -H 'Pragma: no-cache' \
  -H 'Cache-Control: no-cache' \
  -H 'sec-ch-ua: "Chromium";v="92", " Not A;Brand";v="99", "Google Chrome";v="92"' \
  -H 'sec-ch-ua-mobile: ?0' \
  -H 'User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36' \
  -H 'kbn-version: 8.0.0' \
  -H 'Content-Type: application/json' \
  -H 'Accept: */*' \
  -H 'Sec-Fetch-Site: same-origin' \
  -H 'Sec-Fetch-Mode: cors' \
  -H 'Sec-Fetch-Dest: empty' \
  -H 'Referer: http://localhost:5620/app/home' \
  -H 'Accept-Language: en-US,en;q=0.9,ru;q=0.8,de;q=0.7' \
  -H 'Cookie: sid=Fe26.2**a172e66c9b93c137755c30298f858f770ffe8809db80031a092a752628ebb4d0*Hgqsv8KwCFgBRAjDsJJPpQ*hZDKzfdiaQEpPeihLSDnH4DChINlnVQsCnwnnYbaLA8ozxJrj4ORsnVH2rh220kai8n9hcwgE_7wYj7TyO6q_zudNtY-vZ0xzhqcA2PEBkXyFMNYkXCXsqUKMwoFTy295qJINoXzl0fx3l3bEGI7TszXxKD3Z-osAayl9SszC5JkIJ0fccxUw_haVzU49t5CEx6oD9vUElSbuYHFZzaAC3rXpLHNNPyfq2Xh6EdgaBq3198ngo-TYk-Od_EGfg9x**7c31316614804d53c3750c3477f79e885b2616e6f790940101d8ef6d5410ce56*PrFefKYVSHZAHZ0exdYiCThJyU_o4iTQuulCLXCIT8M' \
  --compressed

I checked multiple commits and it is caused by #107350

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)