Fix Wait_Device_Fully_Removed querying the wrong URL

When the device data is gone (device was disconnectd) but
the connector itself is still there, the keyword thinks the
device is no longer there and exits but the device is still
there and might stay due to a bug. Fix this by shortening the
URL to refer to the root of the connector, that should catch
such bugs.

Change-Id: Iddf55b3e5842e50828a327f4b442d0a6bd126e7f
Signed-off-by: Jozef Behran <jbehran@cisco.com>