[bcmsh]: add inactivity timeout for bcmsh (default 300 seconds) (#1921)

Signed-off-by: Guohan Lu <gulv@microsoft.com>

platform/broadcom/docker-syncd-brcm/bcmsh

@@ -1,24 +1,29 @@
 #!/bin/bash
-usage="$(basename "$0") [-h] [-q] -- interactive shell for bcm service
+usage="$(basename "$0") [-h] [-q] [-t timeout] -- interactive shell for bcm service
 
 where:
     -h  show this help text
+    -t  inactivity timeout in seconds (default 300 seconds, 0 for no timeout)
     -q  quite, no banner (default: verbose)"
 
 banner="Press Enter to show prompt.
 Press Ctrl+C to exit.
+NOTICE: Only one bcmsh or bcmcmd can connect to the shell at same time.
 "
 
 # Default verbose
 quiet=false
+timeout=300
 
-while getopts 'hq' option; do
+while getopts 'hqt:' option; do
   case "$option" in
     h) echo "$usage"
        exit
        ;;
     q) quiet=true
        ;;
+    t) timeout=$OPTARG
+       ;;
    \?) printf "illegal option: -%s\n" "$OPTARG" >&2
        echo "$usage" >&2
        exit 1
@@ -31,5 +36,5 @@ if [ "$quiet" = false ]; then
     echo "$banner"
 fi
 
-/usr/bin/socat readline UNIX-CONNECT:/var/run/sswsyncd/sswsyncd.socket
+/usr/bin/socat -T$timeout readline UNIX-CONNECT:/var/run/sswsyncd/sswsyncd.socket