Using relative path for personality file in rebuild server test.

Personality files with absolute paths e.g /etc/rebuild.txt breaks on the test
cirros image. This is because cirros has an empty root filesystem.

fixes lp 1187629

Change-Id: I5b2b37224b722686c3163214fbd53227ac9ce49f
diff --git a/tempest/api/compute/servers/test_server_actions.py b/tempest/api/compute/servers/test_server_actions.py
index 9f97f4f..98620b1 100644
--- a/tempest/api/compute/servers/test_server_actions.py
+++ b/tempest/api/compute/servers/test_server_actions.py
@@ -112,7 +112,7 @@
         meta = {'rebuild': 'server'}
         new_name = rand_name('server')
         file_contents = 'Test server rebuild.'
-        personality = [{'path': '/etc/rebuild.txt',
+        personality = [{'path': 'rebuild.txt',
                        'contents': base64.b64encode(file_contents)}]
         password = 'rebuildPassw0rd'
         resp, rebuilt_server = self.client.rebuild(self.server_id,