Issue 643: Fixing intermittent upgrade failure

[anishakj]

Change log description

Fixing intermittent upgrade failure of pravega.
Added some more conditions to handle error scenarios

Purpose of the change

Fixes #643

What the code does

while during segmentstore update, it fails to get the pod sometimes. Issue is happening because while it tries to get an outdated pod, it has already updated. So added more checks to post error only if all pods were not updated

How to verify it

Peformed upgrade multiple time and issue is not seen

[codecov-commenter]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (2d60c29) 82.37% compared to head (3986b90) 82.27%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #672      +/-   ##
==========================================
- Coverage   82.37%   82.27%   -0.10%     
==========================================
  Files          17       17              
  Lines        4130     4136       +6     
==========================================
+ Hits         3402     3403       +1     
- Misses        583      586       +3     
- Partials      145      147       +2     

Files	Coverage Δ
controllers/upgrade.go	72.04% <16.66%> (-0.77%)	⬇️

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[krishan-Rai]

LGTM