Use different file content to test max_number_personality_files

In test_can_create_server_with_max_number_personality_files,
the max number of personality files are created with the same
content, we can use different file contents to make the testcase
more accurate.

Change-Id: Id572d6d0b7e705bfa075074eeed20de338dbd3fc
diff --git a/tempest/api/compute/servers/test_server_personality.py b/tempest/api/compute/servers/test_server_personality.py
index e5ad7b4..1a5174b 100644
--- a/tempest/api/compute/servers/test_server_personality.py
+++ b/tempest/api/compute/servers/test_server_personality.py
@@ -121,7 +121,7 @@
             path = '/etc/test' + str(i) + '.txt'
             person.append({
                 'path': path,
-                'contents': base64.encode_as_text(file_contents),
+                'contents': base64.encode_as_text(file_contents + str(i)),
             })
         password = data_utils.rand_password()
         created_server = self.create_test_server(personality=person,