Use the full string for localisation

Concatenating localized strings is bound to be confusing.
Give the full string so that translations can be tuned accordingly.

Change-Id: I84a5fa2939c02add5468c4ab4b6f2c4ea1a5f8f0
Abstract add_timestamp out of ComputeDriverCPUMonitor class

Move add_timestamp decorator into ResourceMonitorBase class,
then other monitor metrics can reuse it.

Change-Id: I060353b9e194b1882549fec07fc2a486aeb1fce0
replace type() to isinstance() in nova

In nova/utils.py, a func use the "type" method to
determine the type. It's bertter to use the "isinstance"
method instead.this bug is fixed in glance:
https://review.openstack.org/#/c/65611/4

Change-Id: I10d25d2308436239c50cf3932c212e22c45f92a8
Closes-Bug: #1267300
Capture exception for JSON load in virt.storage_users

If CONF.instances_path/compute_nodes is empty when the storage_users
tries to register the storage use (virt.storage_users.register_storage_use)
the exception is uncaught and raised. As a consequence, the image cache
manager won't run.

Closes-Bug: #1252659

Change-Id: If9ed5e75b0bc0b8f3a7c5fd7ec88f6399e4e59c6
Error message is malformed when removing a sec group from an instance

In the current code the Error message string for a security group which is not
associated with an instance does not get expanded correctly, resulting in users
getting a message:

ERROR: [u'Security group %(security_group_name)s not assocaited with the
instance %(instance)s', {u'instance': u'71069945-5bea-4d53-b6ab-9026bfeebba4',
u'security_group_name': u'phil'}]

In addition fix a minor typo in this message, and clean up a few cases where
error messages are not being passed through _() for i18n.

Change-Id: I85856a135a62bc3415a355e0900ea12ea55f73ae
Closes-Bug: #1273266
Merge "Abstract add_timestamp out of ComputeDriverCPUMonitor class"
Merge "Use the full string for localisation"
Merge "Error message is malformed when removing a sec group from an instance"
Merge "replace type() to isinstance() in nova"
Merge "Capture exception for JSON load in virt.storage_users"
Merge commit 'refs/changes/97/66597/4' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/79/69879/3' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch