Fix is_enabled not work with reload

[bincherry]

fix #1677

1. Rules with is_enabled: false should alse be loaded, but into disabled_rules[]
2. When a old rule is loaded with is_enabled: false, it should be remove from scheduler

[bincherry]

also fix #2893 #2043

tested:

1. started with empty rules
2. add role with is_enabled: true
3. edit that role with is_enabled: false
4. edit that role with is_enabled: true

INFO:elastalert:Starting up
INFO:elastalert:Disabled rules are: []
INFO:elastalert:Sleeping for 59.999757 seconds
INFO:elastalert:Background configuration change check run at 2020-11-12 01:36 UTC
INFO:elastalert:Background alerts thread 0 pending alerts sent at 2020-11-12 01:36 UTC
INFO:elastalert:Disabled rules are: []
INFO:elastalert:Sleeping for 59.999793 seconds
INFO:elastalert:Background configuration change check run at 2020-11-12 01:37 UTC
INFO:elastalert:Background alerts thread 0 pending alerts sent at 2020-11-12 01:37 UTC
INFO:elastalert:Disabled rules are: []
INFO:elastalert:Sleeping for 59.999792 seconds
INFO:elastalert:Background alerts thread 0 pending alerts sent at 2020-11-12 01:38 UTC
INFO:elastalert:Loaded new rule /opt/rules/aaa.yaml
INFO:elastalert:Background configuration change check run at 2020-11-12 01:38 UTC
INFO:elastalert:Disabled rules are: []
INFO:elastalert:Sleeping for 59.999738 seconds
INFO:elastalert:Queried rule aaa from 2020-11-12 01:33 UTC to 2020-11-12 01:38 UTC: 0 / 0 hits
INFO:elastalert:Ran aaa from 2020-11-12 01:33 UTC to 2020-11-12 01:38 UTC: 0 query hits (0 already seen), 0 matches, 0 alerts sent
INFO:elastalert:Rule file /opt/rules/aaa.yaml is now disabled.
INFO:elastalert:Background configuration change check run at 2020-11-12 01:39 UTC
INFO:elastalert:Background alerts thread 0 pending alerts sent at 2020-11-12 01:39 UTC
INFO:elastalert:Disabled rules are: ['aaa']
INFO:elastalert:Sleeping for 59.999752 seconds
INFO:elastalert:Reloading configuration for rule /opt/rules/aaa.yaml
INFO:elastalert:Background alerts thread 0 pending alerts sent at 2020-11-12 01:40 UTC
INFO:elastalert:Background configuration change check run at 2020-11-12 01:40 UTC
INFO:elastalert:Disabled rules are: []
INFO:elastalert:Sleeping for 59.999739 seconds
INFO:elastalert:Queried rule aaa from 2020-11-12 01:38 UTC to 2020-11-12 01:40 UTC: 0 / 0 hits
INFO:elastalert:Ran aaa from 2020-11-12 01:38 UTC to 2020-11-12 01:40 UTC: 0 query hits (0 already seen), 0 matches, 0 alerts sent

[nsano-rururu]

Merged into elastalert2
jertel/elastalert2#31