fix: handle old rest endpoint

[alex-sl-eng]

https://zanata.atlassian.net/browse/ZNTA-2178

JIRA issue URL: paste URL here

[Add a short description of what is changed here.]

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This change is 

[codecov]

Codecov Report

Merging #489 into master will decrease coverage by 0.01%.
The diff coverage is 23.15%.

@@             Coverage Diff              @@
##             master     #489      +/-   ##
============================================
- Coverage     32.95%   32.94%   -0.02%     
  Complexity     5629     5629              
============================================
  Files          1534     1534              
  Lines         64854    64859       +5     
  Branches       7364     7364              
============================================
- Hits          21375    21370       -5     
- Misses        41596    41613      +17     
+ Partials       1883     1876       -7

Impacted Files	Coverage Δ	Complexity Δ
...a/org/zanata/rest/client/ResponseStatusFilter.java	13.63% <0%> (ø)	4 <0> (ø)	⬇️
...g/zanata/rest/client/StatisticsResourceClient.java	71.92% <0%> (-1.76%)	5 <0> (ø)
...rg/zanata/rest/client/SourceDocResourceClient.java	53.62% <14.28%> (-6.08%)	6 <0> (ø)
...org/zanata/rest/client/TransDocResourceClient.java	62.85% <27.77%> (-2.86%)	3 <0> (ø)
...ava/org/zanata/rest/client/AsyncProcessClient.java	45.78% <46.15%> (-1.72%)	4 <0> (ø)

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[alex-sl-eng]

The issue can be reproduced by using 4.3.0-SNAPSHOT client (pull) against older Zanata server (e.g. translate.zanata.org)