UCX osc: re-use value returned by cswap to save additional get

Signed-off-by: Joseph Schuchart <schuchart@hlrs.de>

ompi/mca/osc/ucx/osc_ucx_comm.c

@@ -417,7 +417,6 @@ static int atomic_op_cswap(
     for (int i = 0; i < origin_count; ++i) {
 
         uint64_t tmp_val;
-        do {
         uint64_t target_val = 0;
 
         // get the value from the origin
@@ -433,6 +432,8 @@ static int atomic_op_cswap(
             return ret;
           }
 
+        do {
+
             tmp_val = target_val;
             // compute the result value
             ompi_op_reduce(op, (void *)origin_addr, &tmp_val, 1, origin_dt);