tasks/workunit.py: when cloning, use --depth=1

Help avoid killing git.ceph.com.  A depth 1 clone takes about
7 seconds, whereas a full one takes about 3:40 (much of it
waiting for the server to create a huge compressed pack)

Signed-off-by: Dan Mick <dan.mick@redhat.com>

qa/tasks/workunit.py

@@ -319,6 +319,7 @@ def _run_tests(ctx, refspec, role, tests, env, subdir=None, timeout=None):
                 run.Raw('&&'),
                 'git',
                 'clone',
+                '--depth=1',
                 git_url,
                 clonedir,
                 run.Raw('&&'),
@@ -344,6 +345,7 @@ def _run_tests(ctx, refspec, role, tests, env, subdir=None, timeout=None):
                 run.Raw('&&'),
                 'git',
                 'clone',
+                '--depth=1',
                 alt_git_url,
                 clonedir,
                 run.Raw('&&'),