[pyramid] Avoid shutting down the repository at exit if it's already shutting down
For install `cubicweb-ctl pyramid` command will explicitly call
`repo.shutdown()` so the atexit hook is redundant. Prevent the latter to be
executed when the repository is already shutting down (otherwise one gets an
assertion error).
### Requirements for tests in various cubicweb/**/test directories. ###
## shared by several test folders
cubicweb-card
docutils
Twisted < 16.0.0
webtest
## cubicweb/test
Pygments
mock
#fyzz XXX pip install fails
cubicweb-file
cubicweb-localperms
cubicweb-tag
## cubicweb/devtools/test
flake8
## cubicweb/hooks/test
psycopg2
## cubicweb/pyramid/test
pyramid >= 1.5.0
waitress >= 0.8.9
wsgicors >= 0.3
pyramid_multiauth
## cubicweb/sobject/test
cubicweb-comment