Fix unit testing script failing to run 0chain.net/smartcontract/dbs/event tests

[devyetii]

Fixes

Unit testing script is not working as 0chain.net/smartcontract/dbs/event need docker within the test environment

Changes

• Install docker within the test environment
• Use host's docker daemon as it's not possible to get docker service running inside the container running zchain_unit_test image. It's built on docker's official Alpine image and this is a known issue here. This is done by mounting docker's socket from the host to the container.
• Add --network=host to the container to be able to the database created during the test setup using localhost as database host.

Need to be mentioned in CHANGELOG.md?

Tests

Tasks to complete before merging PR:

• Ensure system tests are passing. If not Run them manually to check for any regressions 📋
• Do any new system tests need added to test this change? do any existing system tests need updated? If so create a PR at 0chain/system_test
• Merge your system tests PR to master AFTER merging this PR

Associated PRs (Link as appropriate):

• blobber:
• gosdk:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...

[codecov-commenter]

Codecov Report

Merging #2375 (4012a27) into staging (893baf7) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff            @@
##           staging    #2375   +/-   ##
========================================
  Coverage    28.96%   28.96%           
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  Files          377      377           
  Lines        63076    63076           
========================================
  Hits         18273    18273           
  Misses       42657    42657           
  Partials      2146     2146           

Flag	Coverage Δ
Unit-Tests	28.96% <ø> (ø)

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see 1 file with indirect coverage changes

[peterlimg]

LGTM