src/meta-openembedded:etcd: don't hardcode /usr/lib in do_install

* I don't know anything about etcd including why we need these binaries duplicated
  in libdir and bindir, but use ${libdir} instead of hardcoded /usr/lib to fix
  do_install with multilib enabled when libdir is /usr/lib64 and it was failing
  with:
  DEBUG: Executing shell function do_install
  ls: cannot access 'etcd/3.5.7-r0/build/bin/linux_arm64/': No such file or directory
  install: cannot stat 'etcd/3.5.7-r0/image/usr/lib/go/src/go.etcd.io/etcd/v3/bin/etcd': No such file or directory
  WARNING: exit code 1 from a shell command.

* the error from ls is unrelated, fixed in:
  https://lists.openembedded.org/g/openembedded-core/message/181269

* also reported on github:
  openembedded/meta-openembedded#616

Signed-off-by: Martin Jansa <[email protected]>
Signed-off-by: Khem Raj <[email protected]>