HDFS-16632. modify block reader finish condition

[chunie]

Description of PR
bytes_to_read_ is used to calculate all the data that client had received（include DATA and META length）. while currently we initialize it to data length，so the stop condition should be:
bytes_to_read_ < 0

JIRA: HADOOP-18204

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	35m 35s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+1 💚	mvninstall	39m 40s		trunk passed
+1 💚	compile	3m 40s		trunk passed
+1 💚	mvnsite	0m 31s		trunk passed
+1 💚	shadedclient	62m 38s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 17s		the patch passed
+1 💚	compile	3m 29s		the patch passed
+1 💚	cc	3m 29s		the patch passed
+1 💚	golang	3m 29s		the patch passed
+1 💚	javac	3m 29s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	mvnsite	0m 18s		the patch passed
+1 💚	shadedclient	18m 27s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	35m 50s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs-native-client.txt	hadoop-hdfs-native-client in the patch failed.
+1 💚	asflicense	0m 37s		The patch does not generate ASF License warnings.
		159m 34s

Reason	Tests
Failed CTEST tests	test_hdfs_ext_hdfspp_test_shim_static

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4185/1/artifact/out/Dockerfile
GITHUB PR	#4185
Optional Tests	dupname asflicense compile cc mvnsite javac unit codespell golang
uname	Linux 39a11da18b7d 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / b3acc08
Default Java	Red Hat, Inc.-1.8.0_322-b06
CTEST	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4185/1/artifact/out/patch-hadoop-hdfs-project_hadoop-hdfs-native-client-ctest.txt
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4185/1/testReport/
Max. process+thread count	692 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs-native-client U: hadoop-hdfs-project/hadoop-hdfs-native-client
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4185/1/console
versions	git=2.9.5 maven=3.6.3
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[jojochuang]

There are tons of WARNING in the ctest output. Would you check if it's related at all?
https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4185/1/artifact/out/patch-hadoop-hdfs-project_hadoop-hdfs-native-client-ctest.txt

[github-actions]

We're closing this stale PR because it has been open for 100 days with no activity. This isn't a judgement on the merit of the PR in any way. It's just a way of keeping the PR queue manageable.
If you feel like this was a mistake, or you would like to continue working on it, please feel free to re-open it and ask for a committer to remove the stale tag and review again.
Thanks all for your contribution.