remove clouds.yaml in clean.sh

devstack failed to install because glance:
Could not determine a suitable URL for the plugin

patch I618ea8e27b49af360c905df85af06d9b1eef8407 tries
to fix this problem, but with a wrong way because path is not
correct, the clouds.yaml is not under /path/to/devstack/~/.config/openstack/
but ~/.config/openstack.

patch I8af6bd465f74099c560dddba6b5221dd79cbc965 tries to
fix this problem, but with a worng way to specify the path,
~$STACK_USER/.config/openstack/clouds.yaml will not expand with
a variable, only const string can.

$ whoami
zqfan
$ touch ~/.config/openstack/clouds.yaml
$ export STACK_USER=zqfan
$ rm -rf ~$STACK_USER/.config/openstack/clouds.yaml
$ ls ~/.config/openstack/
clouds.yaml

Change-Id: I549817d2f4638be615991c1726b39d270ba71357
ref: I618ea8e27b49af360c905df85af06d9b1eef8407
diff --git a/functions-common b/functions-common
index 0806681..a4711dd 100644
--- a/functions-common
+++ b/functions-common
@@ -123,7 +123,7 @@
         --os-project-name admin
 
     # CLean up any old clouds.yaml files we had laying around
-    rm -f ~$STACK_USER/.config/openstack/clouds.yaml
+    rm -f $(eval echo ~"$STACK_USER")/.config/openstack/clouds.yaml
 }
 
 # trueorfalse <True|False> <VAR>