Changes

stream_cli: Explicitly ignore return code of stream_cli_close

Make coverity happy.
We don't really case about th return code of the stream_cli_close()
function in the code path, since the return value is only used
internally/privately in the object and there's no further access/use of
the object after calling it in osmo_stream_cli_close().

Take the chance to update syntax of one return code check to match more
similarly other return checks of the same function.

Related: Coverity CID#435092
Change-Id: Ia6c9e3ca3af08b386f017460b0a0210ed756a929