redfish: managers: fix loop exit condition for verify maximum bmc dump

Symptom:
"Verify Maximum BMC Dump Creation" test item got failed.

Root cause:
According design of phosphor-debug-collector, the maximum dump allowed space for dump is 1024 (BMC_DUMP_TOTAL_SIZE)
There is another requirement, the minimum space required for one bmc dump is 20 (BMC_DUMP_MIN_SPACE_REQD)
However, the loop exit condition only consider the maximum in test item "Verify Maximum BMC Dump Creation".
Thus, the keyword "Create User Initiated BMC Dump" in the loop return fail then cause test got failed.

Solution:
Modify loop exit condition to consider minimum space requirement according dump manager design.

Tested:
robot -t Verify_Maximum_BMC_Dump_Creation redfish/managers/test_bmc_dumps.robot
Verify Maximum BMC Dump Creation :: Create maximum BMC dump and ve... | PASS |
1 test total, 1 passed, 0 failed

Signed-off-by: Tim Lee <timlee660101@gmail.com>
Change-Id: I68306894033bfd5883f984679c1f8cfb4a443775
diff --git a/redfish/managers/test_bmc_dumps.robot b/redfish/managers/test_bmc_dumps.robot
index 141b694..c6290b9 100644
--- a/redfish/managers/test_bmc_dumps.robot
+++ b/redfish/managers/test_bmc_dumps.robot
@@ -9,6 +9,13 @@
 Test Setup          Redfish Delete All BMC Dumps
 Test Teardown       Test Teardown Execution
 
+*** Variables ***
+
+# Total size of the dump in kilo bytes
+${BMC_DUMP_TOTAL_SIZE}       ${1024}
+
+# Minimum space required for one bmc dump in kilo bytes
+${BMC_DUMP_MIN_SPACE_REQD}   ${20}
 
 *** Test Cases ***
 
@@ -159,7 +166,7 @@
     FOR  ${n}  IN RANGE  0  20
       Create User Initiated BMC Dump
       ${dump_space}=  Get Disk Usage For Dumps
-      Exit For Loop If  ${dump_space} >= 1024
+      Exit For Loop If  ${dump_space} >= (${BMC_DUMP_TOTAL_SIZE} - ${BMC_DUMP_MIN_SPACE_REQD})
     END
 
     # Check error while creating dump when dump size is full.