Copy blueprints used for testing to temporary directory

If trying to execute test_cli.sh inside a git checkout
we are going to get the following exception:

Traceback (most recent call last):
  File "./src/sbin/lorax-composer", line 251, in <module>
    repo = open_or_create_repo(server.config["REPO_DIR"])
  File "/home/jenkins/lorax/src/pylorax/api/recipes.py", line 306, in open_or_create_repo
gi.repository.GLib.Error: ggit-error: failed to stat '/home/jenkins/lorax/tests/pylorax/blueprints': Permission denied (-1)
Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib64/python3.7/multiprocessing/popen_fork.py", line 54, in _send_signal
    os.kill(self.pid, sig)

From what I can tell open_or_create_repo() is trying to initialize
a git repository inside the blueprints directory which fails when
we have an active git checkout.

This doesn't happen when we run the tests in Travis CI because
rsync excludes .git/ inside the Docker container.

(cherry picked from commit c9d706a382)

tests/test_cli.sh

@@ -6,8 +6,11 @@ rm -rf /var/tmp/beakerlib-*/
 export top_srcdir=`pwd`
 . ./tests/testenv.sh
 
+BLUEPRINTS_DIR=`mktemp -d '/tmp/blueprints.XXXXX'`
+cp ./tests/pylorax/blueprints/*.toml $BLUEPRINTS_DIR
+
 # start the lorax-composer daemon
-./src/sbin/lorax-composer --sharedir ./share/ ./tests/pylorax/blueprints/ &
+./src/sbin/lorax-composer --sharedir ./share/ $BLUEPRINTS_DIR &
 
 # wait for the backend to become ready
 tries=0