test//osd/osd-copy-from.sh: use absolute path for "rados put"

"rados -p rbd put foo rados" does not work if "rados" is not in current
path. so change it to "rados -p rbd put foo $(which rados)"

Signed-off-by: Kefu Chai <kchai@redhat.com>

src/test/osd/osd-copy-from.sh

@@ -45,7 +45,7 @@ function TEST_copy_from() {
     run_osd $dir 1 || return 1
 
     # success
-    rados -p rbd put foo rados
+    rados -p rbd put foo $(which rados)
     rados -p rbd cp foo foo2
     rados -p rbd stat foo2