Commits integrates monasca-agent with monascaclient,
that is currently using osc-lib. That requires some
changes in the initialization model of the client.
Details:
* no need to check if token has expired (underlying library
[osc-lib] will request new token if it is about to expire
* initializing the client happens once therefore keystone.Keystone
instance can be created lazily (it is singleton, so it might happen
it is already available)
Extra:
* marked all variables as private
Depends-On: I1712a24739438e2d8331a495f18f357749a633c5
Depends-On: Iec97e50089ed31ae7ad8244b37cec128817871a5
Depends-On: I579f6bcd5975a32af2a255be41c9b6c4043fa1dc
Change-Id: Ifee5b88ccb632222310aafb1081ecb9c9d085150