[ignite] Need to downgrade to JDK 8, by ignite docker restriction

[yanmo96]

When deploy Ignite, need to change the following files to use JDK 8.
Reason being the Docker image we use apacheignite/ignite:2.10.0 have JDK 8 in it.

Bellow are some of the files need to change during deployment process:

• sed -i 's/<java.version>11</java.version>/<java.version>8</java.version>/g' /root/alcor/lib/pom.xml
• sed -i 's/11</source>/8</source>/g' /root/alcor/lib/pom.xml
• sed -i 's/11</target>/8</target>/g' /root/alcor/lib/pom.xml

Later we may host our own custom build image, or ignite may upgrade their image with new JDK version

[xieus]

@pkommoju This is a good question to raise to Ignite community regarding (1) why JDK 8 remains in use; (2) any plan to upgrade to JDK 11 and above (3) best practice of using newer JDK with Ignite.