gpcheckperf: fixing string parsing in parseMultiDDResult()

Issue:
After updating gpssh to return string output, gpcheckperf failed to parse results.

RCA:
String before gpssh changes: "'multidd total bytes '"
String after gpssh fix: "multidd total bytes '"
In parseMultiDDResult(), str.Find() before gpssh changes were returning index 1
as it was getting string starting with "'".
Post gpssh changes, substring is as the beginning of the string hence returning index 0.

Fix:
str.find() returns -1 if the substring is not found otherwise returns index.
As the substring searched in parseMultiDDResult() is appearing at index zero,
corrected condition to include index zero.

Author: piyushc01

gpMgmt/bin/gpcheckperf

@@ -420,7 +420,7 @@ def parseMultiDDResult(out):
         o = line[i + 2:]
 
 
-        if o.find('multidd total bytes ') > 0:
+        if o.find('multidd total bytes ') >= 0:
             h = line[1:i]
             o = o.split()
             m = re.search("(^\d+)", o[-1])
@@ -429,7 +429,7 @@ def parseMultiDDResult(out):
             bytes = int(m.group(1))
             continue
 
-        if o.find('real') > 0:
+        if o.find('real') >= 0:
             h = line[1:i]
             o = o.split()
             m = re.search("(^\d+.\d+)", o[1])