[improve] A more universal method to detect java8

[Shawyeok]

The current bookkeeper installation package's scripts in the bin directory depend on JAVA_HOME to detect whether the current Java runtime environment is Java 8. However, in some deployment scenarios, the system does not configure the JAVA_HOME environment variable. If Java 11 or a higher version is installed, running the script will result in the following error:

# yum install java-11-openjdk-devel
# bin/bookkeeper shell
JAVA_HOME not set, using java from PATH. (/usr/bin/java)
OpenJDK 64-Bit Server VM warning: Option AggressiveOpts was deprecated in version 11.0 and will likely be removed in a future release.
Unrecognized VM option 'PrintGCApplicationStoppedTime'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

This patch provides a more universal method to detect whether the runtime environment is Java 8, while avoiding the restriction of forcing users to set the JAVA_HOME variable.

[lhotari]

LGTM.

If there's a need to detect the major version, Pulsar uses this approach for detecting the major version: https://github.com/apache/pulsar/blob/9c7716ce12b1905cbe4c95fb87a623c70b694085/conf/pulsar_env.sh#L55-L68

[lhotari]

Thanks for this PR @Shawyeok . I have already applied this change as part of the changes for fixing the CI in #4197. It was one of the problems there.
It's already in master branch:

bookkeeper/bin/common.sh

Lines 71 to 78 in 7bd91a7

	detect_jdk8() {
	local is_java_8=$($JAVA -version 2>&1 | grep version | grep '"1\.8')
	if [ -z "$is_java_8" ]; then
	echo "0"
	else
	echo "1"
	fi
	}

[Shawyeok]

@lhotari
Thanks, I'm going to close this one.