[BEAM-1950] Add missing 'static' keyword to MicrobatchSource#initReaderCache

[aviemzur]

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[aviemzur]

R: @staslev

[staslev]

LGTM (pending tests).

[asfbot]

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[coveralls]

Coverage increased (+0.007%) to 70.576% when pulling 5751c0d on aviemzur:fix-microbatchsource-readercache-lock into 571631a on apache:master.

[asfbot]

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Failed Tests: 1

beam_PreCommit_Java_MavenInstall/org.apache.beam:beam-runners-spark: 1

• org.apache.beam.runners.spark.translation.streaming.CreateStreamTest.testLateDataAccumulating

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[coveralls]

Coverage increased (+0.008%) to 70.576% when pulling 5751c0d on aviemzur:fix-microbatchsource-readercache-lock into 571631a on apache:master.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
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Failed Tests: 1

beam_PreCommit_Java_MavenInstall/org.apache.beam:beam-sdks-java-io-hbase: 1

• org.apache.beam.sdk.io.hbase.HBaseIOTest.testWritingFailsTableDoesNotExist

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[asfbot]

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[coveralls]

Coverage decreased (-0.5%) to 70.096% when pulling 5751c0d on aviemzur:fix-microbatchsource-readercache-lock into 571631a on apache:master.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
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