exchange: use command executor for getbundle
The code consuming the bundle has been moved to inside the
context manager, as that is supposed to be part of the API.
(Although it doesn't matter for version 1 peers.)
Differential Revision: https://phab.mercurial-scm.org/D3316
# This config file points Mercurial at the system-wide certificate
# store from the ca-certificates package.
[web]
cacerts = /etc/ssl/certs/ca-certificates.crt