Excavator: Upgrade dependencies (apache#485)

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Changes produced by the versions-props/upgrade-all check.

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Author: svc-excavator-bot

versions.props

@@ -17,7 +17,7 @@
 
 org.apache.commons:commons-compress = 1.18
 commons-io:commons-io = 2.6
-com.spotify:docker-client = 8.14.5
+com.spotify:docker-client = 8.15.0
 org.assertj:assertj-core = 3.11.1
-org.mockito:mockito-core = 2.23.4
+org.mockito:mockito-core = 2.24.0
 junit:junit = 4.12