Client nonces are not verified

[mlgiraud]

Description

According to the standard the nonces need to have a certain length. Currently this does not seem to be checked anywhere.
See spec Part 4 v1.03 Table 10

I will create a fix and write some unit tests when I have time so this issue doesn't appear again.

Checklist

Please provide the following information:

• open62541 Version (release number or git tag): master
• Critical issue