test: retry "get nodes that match regex" test

[jackfrancis]

Reason for Change:

Observed this E2E flake:

$ k get nodes -o json
 �Failure [30.437 seconds]�
 2019/10/07 21:04:48 Error trying to run 'kubectl get nodes':
  - exit status 1
 2019/10/07 21:04:48 
  - {
     "apiVersion": "v1",
     "items": [],
     "kind": "List",
     "metadata": {
         "resourceVersion": "",
         "selfLink": ""
     }
 }
 Unable to connect to the server: dial tcp 13.81.26.234:443: i/o timeout
 �[BeforeSuite] BeforeSuite �[0m
 �/go/src/github.com/Azure/aks-engine/test/e2e/kubernetes/kubernetes_test.go:71�
 
   �Expected error:
       <*exec.ExitError | 0xc0003cbc40>: {
           ProcessState: {
               pid: 3198,
               status: 256,
               rusage: {
                   Utime: {Sec: 0, Usec: 150474},
                   Stime: {Sec: 0, Usec: 22361},
                   Maxrss: 37936,
                   Ixrss: 0,
                   Idrss: 0,
                   Isrss: 0,
                   Minflt: 3460,
                   Majflt: 0,
                   Nswap: 0,
                   Inblock: 0,
                   Oublock: 8,
                   Msgsnd: 0,
                   Msgrcv: 0,
                   Nsignals: 0,
                   Nvcsw: 349,
                   Nivcsw: 229,
               },
           },
           Stderr: nil,
       }
       exit status 1
   not to have occurred�
 
   /go/src/github.com/Azure/aks-engine/test/e2e/kubernetes/kubernetes_test.go:93

Issue Fixed:

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[codecov]

Codecov Report

Merging #2120 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2120   +/-   ##
=======================================
  Coverage   76.58%   76.58%           
=======================================
  Files         135      135           
  Lines       20613    20613           
=======================================
  Hits        15787    15787           
  Misses       3903     3903           
  Partials      923      923

[mboersma]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jackfrancis, mboersma

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[acs-bot]

New changes are detected. LGTM label has been removed.