Remove unnecessary executable permissions

This commit removes unnecessary executable permissions. I found them
with find command[1].

[1] $ find tempest -type f -executable

Change-Id: Ife03bb46893ed39ac0b236bf42351c408d739e7a
diff --git a/tempest/api/identity/v3/test_catalog.py b/tempest/api/identity/v3/test_catalog.py
old mode 100755
new mode 100644
diff --git a/tempest/api/volume/admin/test_user_messages.py b/tempest/api/volume/admin/test_user_messages.py
old mode 100755
new mode 100644
diff --git a/tempest/lib/services/volume/v1/encryption_types_client.py b/tempest/lib/services/volume/v1/encryption_types_client.py
old mode 100755
new mode 100644
diff --git a/tempest/lib/services/volume/v2/encryption_types_client.py b/tempest/lib/services/volume/v2/encryption_types_client.py
old mode 100755
new mode 100644