This checks that all ES plugins and xplugins are installed. I also
changed the rest check to be a simple plugin count, so it does not fail
when new plugins are added.
Original commit: elastic/x-pack-elasticsearch@eaab182e43
For now this just tries to install license, marvel and watcher, and then checks
that these plugins are listed in the node infos. I can do shield once I figure
out how to set it up for REST tests.
Original commit: elastic/x-pack-elasticsearch@8549f4bc5a
Nik Everett
Ryan Ernst
jaymode
Martijn van Groningen
Adrien Grand