weldr-client has replaced composer-cli so remove all of the code and
tests, adjust various things so they don't expect it to be available,
and rename some things like test/composertest.py to reflect its
exclusive use by lorax.
(cherry picked from commit b75b692607)
When monitoring log output in livemedia-creator --no-virt it could get
stuck if the output from anaconda stops for some reason.
This changes execReadlines so that it will only read output when it is
available, will monitor the process state, and continue to call the
callback function.
It also adds a final timeout on proc.communicate() so that if Anaconda
becomes stuck and won't exit livemedia-creator will eventually exit.
When the no-virt callback terminates anaconda on an error it now sends a
TERM signal to all of the unshare process' children because just sending
it to unshare doesn't cause anaconda to exit.
