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

[wenchaozhang-123]

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

fix #ISSUE_Number

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[my-ship-it]

LGTM