Fix mutable config in manila-scheduler

We had SIGHUP apply the "mutate" behavior to the
ProcessLauncher with [1], however, the scheduler
process does not use ProcessLauncher.

Oslo config made "debug" a mutable config option
in [3]

Closes-Bug: #1785129

[1] I6499ae6c98d9489a123bb20febd6c1ddb9e17b86
[3] I1e7a69de169cc85f4c09954b2f46ce2da7106d90

Change-Id: Ifffe3cad0f5cd52988ce253794efc5b03ea9840b

manila/service.py

@@ -383,7 +383,8 @@ def serve(server, workers=None):
     global _launcher
     if _launcher:
         raise RuntimeError('serve() can only be called once')
-    _launcher = service.launch(CONF, server, workers=workers)
+    _launcher = service.launch(CONF, server, workers=workers,
+                               restart_method='mutate')
 
 
 def wait():

releasenotes/notes/bug-1785129-fix-sighup-behavior-with-scheduler-8ee803ad0e543cce.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - The SIGHUP behavior for the manila-scheduler service has been fixed.
+    Previously, only the manila-share service was responding to SIGHUP and
+    reloading its configuration, now manila-scheduler does the same.