release/v20.03: Update badger 06/09/2020

[dgraph-bot]

This PR updates badger. The important changes are

KeepL0InMemory -> Set to false (badger default)
DetectConflicts -> Set to false

This change is 

Docs Preview:

[jarifibrahim]

This update contains conflict detection changes in badger. We need to disable the flag.

Reviewable status: 0 of 2 files reviewed, all discussions resolved (waiting on @manishrjain)

[jarifibrahim]

Reviewable status: 0 of 3 files reviewed, all discussions resolved (waiting on @manishrjain)

[peter-hartmann-emrsn]

To decide if I want to include this fix into my testing, it'd be good to know what problem it'll fix.

[jarifibrahim]

@peter-hartmann-emrsn There's the changelog of this PR. There are two important changes

• KeepL0InMemory set to false -> This would allow dgraph to start faster in case of a crash.
• Deleted/Expired keys in compaction -> This fixes a bug where deleted/expired keys were not purged from the system,

This description was generated using this script:

#!/bin/bash

set -e
GHORG=${GHORG:-dgraph-io}
GHREPO=${GHREPO:-badger}
cat <<EOF
This description was generated using this script:
\`\`\`sh
`cat $0`
\`\`\`
Invoked as:

    `echo GHORG=${GHORG} GHREPO=${GHREPO} $(basename $0) ${@:1}`

EOF
git log --oneline --reverse ${@:1} \
  | sed -E "s/^(\S{7}\s)//g" \
  | sed -E "s/([\s|\(| ])#([0-9]+)/\1${GHORG}\/${GHREPO}#\2/g" \

Invoked as:

GHORG=dgraph-io GHREPO=badger changes.sh e7b6e76f96e8...14386ac9b764

DefaultOptions: Set KeepL0InMemory to false (dgraph-io/badger#1345)
Add immudb to the project list (dgraph-io/badger#1341)
Iterator: Always add key to txn.reads (dgraph-io/badger#1328)
StreamWriter: Close head writer (dgraph-io/badger#1347)
Fix build on golang tip (dgraph-io/badger#1355)
Compaction: Expired keys and delete markers are never purged (dgraph-io/badger#1354)
Support disabling conflict detection (dgraph-io/badger#1344)
Tests: Do not leave behind state goroutines (dgraph-io/badger#1349)
Restore: Account for value size as well (dgraph-io/badger#1358)
GC: Consider size of value while rewriting (dgraph-io/badger#1357)