Fix ES6 Migration Tool data index mapping name and Refresh before Reindex

[lorthirk]

After merging #3135, there were a couple of issues:

• The mapping type for the Data Messages Index was wrong (because the ES client always returned _doc instead of message)
• The reindex operations could fail without refreshing the indexes

Related Issue
No related issues

[codecov]

Codecov Report

Merging #3157 (16bdde5) into develop (bb8ed2c) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##             develop    #3157      +/-   ##
=============================================
- Coverage      63.00%   62.96%   -0.05%     
+ Complexity      2490     2486       -4     
=============================================
  Files           1118     1118              
  Lines          23138    23138              
  Branches        2000     2000              
=============================================
- Hits           14579    14569      -10     
- Misses          7644     7653       +9     
- Partials         915      916       +1     

Impacted Files	Coverage Δ	Complexity Δ
...ransport/mqtt/pooling/PooledMqttClientFactory.java	61.90% <0.00%> (-9.53%)	0.00% <0.00%> (ø%)
...a/org/eclipse/kapua/transport/mqtt/MqttClient.java	56.09% <0.00%> (-6.10%)	0.00% <0.00%> (ø%)
...obDeviceManagementOperationManagerServiceImpl.java	73.17% <0.00%> (-3.66%)	13.00% <0.00%> (-1.00%)
.../DeviceManagementOperationRegistryServiceImpl.java	66.07% <0.00%> (-3.58%)	12.00% <0.00%> (-2.00%)
...ob/execution/internal/JobExecutionServiceImpl.java	100.00% <0.00%> (ø)	15.00% <0.00%> (ø%)
...ua/broker/core/listener/DeviceMessageListener.java	67.44% <0.00%> (+6.97%)	0.00% <0.00%> (ø%)
...lugin/authentication/AdminAuthenticationLogic.java	78.57% <0.00%> (+7.14%)	0.00% <0.00%> (ø%)