HACK wip context improvement
mds: abstract base MDSContext

This is so that subsystems can define MDSInternalContextBase
and MDSIOContextBase subclasses that get the MDS* pointer in
a convenient way (without a redudant MDS* attribute on the context
class).

Signed-off-by: John Spray <john.spray@redhat.com>
mds: add MDCacheIOContext

To make the _IO_ Context subclasses explicitly
descendents of MDSIOContext.

Signed-off-by: John Spray <john.spray@redhat.com>
osdc/Journaler: fix finishers for objecter ops

Had missed these when adding them to filer calls.

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
mds: make RecoveryQueue context an IOContext

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
osdc/Journaler: reprobe should be private

...and as such does not need to take lock itself

Signed-off-by: John Spray <john.spray@redhat.com>
common: assert non-null ptrs in OnFinisher

Callers should not be constructing C_OnFinisher
if they have no context to call back.

Signed-off-by: John Spray <john.spray@redhat.com>
mds: assert non-null in IO_Wrapper

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
mds/MDLog: avoid passing null into IO_Wrapper

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
mds: ctx used with journaler should be IOContext

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
mds: squash last few non-IO bare Contexts

Signed-off-by: John Spray <john.spray@redhat.com>
mds: fix malformed MDSInternalContext constructor

...and switch to MDCacheContext while we're at it.

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
mds/Migrator: assert ptrs in constructor

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>
mds/MDSContext: debug log RTTI context class

Because otherwise on an assertion failure it's not obvious
what kind of Context we were handling when it went down.

Signed-off-by: John Spray <john.spray@redhat.com>
mds: fix ImportDirLoggedStart

...and get rid of no-longer needed default
constructor for MDSInternalContext.

Squash me!

Signed-off-by: John Spray <john.spray@redhat.com>