ynh_redis_remove_db should remove only the current database

[PatBriPerso]

Problem

• ynh_redis_remove_db remove all databases

Solution

• use flushdb instead of flushall to remove only the current database

As you can see below:

$ redis-cli
127.0.0.1:6379> help FLUSHALL
  FLUSHALL [ASYNC]
  summary: Remove all keys from all databases
  since: 1.0.0
  group: server
127.0.0.1:6379> help FLUSHDB
  FLUSHDB [ASYNC]
  summary: Remove all keys from the current database
  since: 1.0.0
  group: server

PR Status

• [X] Code finished and ready to be reviewed/tested
• [ ] The fix/enhancement were manually tested (if applicable)

Automatic tests

Automatic tests can be triggered on https://ci-apps-dev.yunohost.org/ after creating the PR, by commenting "!testme", "!gogogadgetoci" or "By the power of systemd, I invoke The Great App CI to test this Pull Request!". (N.B. : for this to work you need to be a member of the Yunohost-Apps organization)

[ericgaspar]

Redis helper is now part of the core and as flushdb instead of flushall. Thanks