RATIS-1680. TestLeaderInstallSnapshot creates untracked files

[adoroszlai]

What changes were proposed in this pull request?

TestLeaderInstallSnapshot leaves untracked files in ratis-test/snapshot directory.

$ mvn clean test -DfailIfNoTests=false -Dtest=TestLeaderInstallSnapshot
...
$ git status
On branch master
Your branch is up to date with 'origin/master'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)

	ratis-test/snapshot/

nothing added to commit but untracked files present (use "git add" to track)

$ find ratis-test/snapshot | sort
ratis-test/snapshot
ratis-test/snapshot/1.bin
ratis-test/snapshot/sub
ratis-test/snapshot/sub/2.bin

The root cause is that getSMdir() returns null until storage is initialized.

https://issues.apache.org/jira/browse/RATIS-1680

How was this patch tested?

$ mvn clean test -DfailIfNoTests=false -Dtest=TestLeaderInstallSnapshot
...
$ git status
On branch RATIS-1680

nothing to commit, working tree clean

Regular CI:
https://github.com/adoroszlai/incubator-ratis/actions/runs/2882163120

[szetszwo]

+1 the change looks good.

Checked it manually. The extra files are in the individual directories.

$find ratis-test/ -name 1.bin
ratis-test//target/test/data/a248a6c8/MiniRaftClusterWithGrpc20890651/s2/06b4977b-37ee-46a9-90bf-f0c8c77cbb49/sm/snapshot/1.bin
ratis-test//target/test/data/a248a6c8/MiniRaftClusterWithGrpc20890651/s1/06b4977b-37ee-46a9-90bf-f0c8c77cbb49/sm/snapshot/1.bin
ratis-test//target/test/data/a248a6c8/MiniRaftClusterWithGrpc20890651/s0/06b4977b-37ee-46a9-90bf-f0c8c77cbb49/sm/snapshot/1.bin
ratis-test//target/test/data/a248a6c8/MiniRaftClusterWithGrpca918d41b/s2/a253e4e5-f13e-42b2-8bc3-039d0995cca3/sm/snapshot/1.bin
ratis-test//target/test/data/a248a6c8/MiniRaftClusterWithGrpca918d41b/s1/a253e4e5-f13e-42b2-8bc3-039d0995cca3/sm/snapshot/1.bin
ratis-test//target/test/data/a248a6c8/MiniRaftClusterWithGrpca918d41b/s0/a253e4e5-f13e-42b2-8bc3-039d0995cca3/sm/snapshot/1.bin

[adoroszlai]

Thanks @szetszwo for reviewing and committing it.