openwsman: pass correct libdir to cmake

Fix QA issue when enable multilib:
ERROR: QA Issue: openwsman: Files/directories were installed but not
shipped in any package:
  /usr/lib
  /usr/lib/libwsman_clientpp.so
  /usr/lib/libwsman_client.so
  /usr/lib/libwsman.so.1.0.0
  /usr/lib/libwsman.so
  /usr/lib/libwsman_client.so.4
  [snip]
Please set FILES such that these items are packaged. Alternatively if they are unneeded, avoid installing them or delete them within do_install. [installed-vs-shipped]

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>