recipes: Replace "cp -a" with "cp -R --no-dereference --preserve=mode,links"

* Using "cp -a" leaks UID of user running the builds, causing
  many QA warnings.
* See this thread for details:
  http://lists.openembedded.org/pipermail/openembedded-core/2015-November/112904.html

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-networking/recipes-protocols/net-snmp/net-snmp_5.7.3.bb

@@ -85,7 +85,7 @@ do_install_ptest() {
     for i in ${S}/dist ${S}/include ${B}/include ${S}/mibs ${S}/configure \
         ${B}/net-snmp-config ${S}/testing; do
         if [ -e "$i" ]; then
-            cp -a "$i" ${D}${PTEST_PATH}
+            cp -R --no-dereference --preserve=mode,links -v "$i" ${D}${PTEST_PATH}
         fi
     done
     echo `autoconf -V|awk '/autoconf/{print $NF}'` > ${D}${PTEST_PATH}/dist/autoconf-version