[swss.sh] optimize macsec feature state query (sonic-net#12946)

- Why I did it
There's a slowdown in bootup related to the execution of a show command during startup of swss service. show is a pretty heavy command and takes long time to execute ~2 sec.

- How I did it
I replaced show with sonic-db-cli which takes a ms to run.

- How to verify it
Boot the switch and verify swss is active.

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

files/scripts/swss.sh

@@ -304,7 +304,7 @@ function check_peer_gbsyncd()
 
 function check_macsec()
 {
-    MACSEC_STATE=`show feature status | grep macsec | awk '{print $2}'`
+    MACSEC_STATE=`$SONIC_DB_CLI CONFIG_DB hget 'FEATURE|macsec' state`
 
     if [[ ${MACSEC_STATE} == 'enabled' ]]; then
         if [ "$DEV" ]; then