Try to increase vm.max_map_count=262144 if not running on a container (else get blocked)

[Alvaro Uria]

ES service won't start because:
"""
[1] bootstrap checks failed
[1]: max virtual memory areas vm.max_map_count [65530] is too low,
increase to at least [262144]
"""

The charm should try to modify the value (and add a /etc/sysctl.d/99-elasticsearch.conf) if it's not a container. Otherwise, charm should get blocked and advice the user to change such value.

[Peter Sabaini (peter-sabaini)]

The PR https://github.com/elastic/elasticsearch/pull/21899 introduces a
knob to prevent ES from demanding vm.max_map_count increases, could also try to set this when running in a container with low vm.max_map_count