permissions-manager: use only one GKeyfileSettingsBackends per process

In combination with the previous commit, which eliminates a
GKeyfileSettingsBackend leak in our settings code and eliminates our
custom GKeyfileSettingsBackend use for web process settings, this should
reduce our use of GKeyfileSettingsBackend as far as possible to ensure
we minimize usage of inotify handles.

Fixes #865
5 jobs for mcatanzaro/#993 in 3 minutes and 51 seconds (queued for 1 second)
Status Job ID Name Coverage
  Check
passed #494615
check-code-style

00:00:59

failed #494616
allowed to fail
cppcheck

00:00:55

 
  Test
passed #494617
flatpak

00:02:15

 
  Deploy
passed #494618
review

00:00:37

manual #494619
allowed to fail manual
stop_review
 
Name Stage Failure
failed
cppcheck Check
[lib/sync/ephy-sync-service.c:478] -> [lib/sync/ephy-sync-crypto.c:61]: (error) Null pointer dereference: nonce
[lib/sync/ephy-sync-service.c:478] -> [lib/sync/ephy-sync-crypto.c:63]: (error) Null pointer dereference: timestamp
[lib/sync/ephy-sync-crypto.c:338] -> [lib/sync/ephy-sync-crypto.c:101]: (error) Null pointer dereference: app
[lib/sync/ephy-sync-crypto.c:338] -> [lib/sync/ephy-sync-crypto.c:102]: (error) Null pointer dereference: dlg
[lib/sync/ephy-sync-crypto.c:338] -> [lib/sync/ephy-sync-crypto.c:103]: (error) Null pointer dereference: ext
[lib/sync/ephy-sync-service.c:1238] -> [lib/sync/ephy-sync-service.c:1061] -> [lib/sync/ephy-sync-service.c:160]: (error) Null pointer dereference: request_body
[lib/sync/ephy-sync-service.c:1500] -> [lib/sync/ephy-sync-service.c:302]: (error) Null pointer dereference: batch_id
(information) Cppcheck cannot find all the include files (use --check-config for details)
ERROR: Job failed: exit code 1