gpssh: removing b and \r getting added to command output

Issue:
This issue applies to 7x only. Gpssh command output contained
byte string and \r characters.

RCA:
When gpssh reads output from pexpect.before, it's in byte format.
Need to convert this output into the string format. Also, there are carriage
return characters (\r) that need to be removed.

Fix:
When the output is returned from gpssh, made sure that we are converting bytes to string.
To remove \r characters, striping the lines.

Sample output before the fix:

$ gpssh -h sdw1 hostname
  [sdw1] b'sdw1\r'

After the fix:
$ gpssh -h sdw1 hostname
 [sdw1] sdw1

gpMgmt/bin/gppylib/util/ssh_utils.py

@@ -283,8 +283,9 @@ def executeCommand(self, command):
 
         for s in self.pxssh_list:
             # Split the output into an array of lines so that we can add text to the beginning of
-            #    each line
-            output = s.before.split(b'\n')
+            # each line. Decoding string as we are getting bytecode string in s.before
+            # Removing \r characters in each line by strip
+            output = [x.strip() for x in s.before.decode().split('\n')]
             output = output[1:-1]
 
             commandoutput.append(output)