NSS: change implementation of IsKnownCA

[Thykof]

Context
Describe / explain why we should do this: motivations, context or other info. Keep it brief and simple - PM

On MacOS, with firefox, we have removed the installation of the nss library used to install the root CA in the nss database that enable https to work on firefox.

If the user install the nss lib manually, he must be able to run the repair mode of massa station in sudo to install the root CA in the nss database.

The problem is that if a CA is already present in the nss database but is not the same saved in /etc/massastation/certs, our current repair mode will detect that the CA is already present, and consequently not install the CA in /etc/massastation/cert, because the comparison is based on the name of the CA, not the content.

We would like to improve the way the repair mode check if the CA is known by the nss database:

station/pkg/nss/certutilservice.go

Line 42 in 3046b23

return s.runner.Run("-V", "-d", dbPath, "-u", "L", "-n", certificateName)

User flow
Describe the user flow using user stories so the end result is super clear - PM

How to
List the step-by-step to get it do if needed - PM

Technical details
Give the technical insights so anyone in the team can tackle the tasks - Dev

QA testing
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