[Non-blocking cosmetic fix] Add missing "&&" into Node definitions when updating yarn

[Chuxel]

Currently the node definitions clear out the /opt/yarn location in the base node images and install yarn using apt-get so it can be upgraded in-place by the user as needed. The code looks like this:

rm -rf /opt/yarn-* \
    rm -f /usr/local/bin/yarn \	   
    rm -f /usr/local/bin/yarnpkg \
    ...

This is wrong, because the last two paths won't be deleted. It should be:

rm -rf /opt/yarn-* \
    && rm -f /usr/local/bin/yarn \	   
    && rm -f /usr/local/bin/yarnpkg \
    ...

However, because /opt/yarn-* is removed, the links in /usr/local/bin are ignored and everything works anyway. So this is more of a cosmetic fix and not blocking.

[chrmarti]

Looks good, but let's hold back on non-essential changes until we lift the lock-down.