meta-google: networking: fix shellcheck warnings

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I7ae5c315d5a938b29c6fd5d68f07225d125ccead
diff --git a/meta-google/recipes-google/networking/gbmc-bridge/gbmc-br-dhcp-term.sh b/meta-google/recipes-google/networking/gbmc-bridge/gbmc-br-dhcp-term.sh
index 46bf136..1ba0ac3 100644
--- a/meta-google/recipes-google/networking/gbmc-bridge/gbmc-br-dhcp-term.sh
+++ b/meta-google/recipes-google/networking/gbmc-bridge/gbmc-br-dhcp-term.sh
@@ -42,7 +42,7 @@
   # Ensure we only complete the addr lookup loop every 10s
   tosleep=$((before + 10 - SECONDS))
   if (( tosleep > 0 )); then
-    sleep $tosleep
+    sleep "$tosleep"
   fi
 done
 
@@ -99,7 +99,7 @@
   w=$((active_ms/1000/1000 + (wait_min*60) - cur_s))
   [ "$w" -lt 0 ] && break
   echo "Waiting ${w}s for DHCP process" >&2
-  sleep $w
+  sleep "$w"
 done
 
 echo "Stopping DHCP processing" >&2