Use binary-deps.d for dracut ramdisks

Instead of hard-coding a list of binaries to include in the dracut
ramdisk, use the existing binary-deps.d functionality to provide a
list.  This will allow other ramdisks (such as discovery) to add
the binaries they need.

Change-Id: Ib7ffa15e08db1cc45e93a8f2a5c01369772c93ff

elements/dracut-ramdisk/binary-deps.d/dracut-ramdisk

@@ -0,0 +1,15 @@
+tail
+head
+awk
+ifconfig
+cut
+expr
+route
+ping
+tgtd
+tgtadm
+nc
+wget
+curl
+tftp
+grep

elements/dracut-ramdisk/post-install.d/99-build-dracut-ramdisk

@@ -51,7 +51,7 @@ cp "$TMP_MOUNT_PATH/init" "$MODULE_PATH/80deploy-ramdisk/init.sh"
 # -o: Force omission of these dracut modules.  Our scripts are written for bash,
 #     so dash is not desirable, and plymouth was causing some issues on Ubuntu.
 dracut -N \
-    --install 'tail head awk ifconfig cut expr route ping tgtd tgtadm nc wget curl tftp grep' \
+    --install "$(cat /etc/dib_binary_deps)" \
     --kernel-cmdline "rd.shell rd.debug rd.neednet=1 rd.driver.pre=ahci" \
     --include "$TMP_MOUNT_PATH/init-func" /init-func \
     --kver "${KERNEL_VERSION}" \