conntrack-tools: add required kernel modules to RRECOMMENDS

Refer to https://git.netfilter.org/conntrack-tools/tree/INSTALL, add
required kernel modules to RRECOMMENDS.

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-networking/recipes-filter/conntrack-tools/conntrack-tools_1.4.7.bb

@@ -54,3 +54,7 @@ pkg_postinst:${PN} () {
 	setcap cap_net_admin+ep "$D/${sbindir}/conntrack"
 }
 PACKAGE_WRITE_DEPS += "libcap-native"
+
+RRECOMMENDS:${PN} = "kernel-module-nf-conntrack kernel-module-nfnetlink \
+                     kernel-module-nf-conntrack-netlink \
+                    "