Add sleep time for IPMI command chassis identify

According to IPMI SPEC section 28.5 Chassis Identify Command.
byte 1 in Request Data: "Identify Interval in seconds. 1-based.
Timing accuracy = -0/+20%".

Signed-off-by: Tony Lee <tony.lee@quantatw.com>
Change-Id: Ifb42de16c6da28fb684f4f33d6dcfadef4406dba
diff --git a/tests/ipmi/test_general_ipmi.robot b/tests/ipmi/test_general_ipmi.robot
index 41248c4..3608174 100755
--- a/tests/ipmi/test_general_ipmi.robot
+++ b/tests/ipmi/test_general_ipmi.robot
@@ -30,14 +30,14 @@
     Run IPMI Standard Command  chassis identify
     Verify Identify LED State  ${1}
 
-    Sleep  15s
+    Sleep  18s
     Verify Identify LED State  ${0}
 
     # Set "chassis identify" to 10s and verify that the LED blinks for 10s.
     Run IPMI Standard Command  chassis identify 10
     Verify Identify LED State  ${1}
 
-    Sleep  10s
+    Sleep  12s
     Verify Identify LED State  ${0}