Improve a bit performance of Ceilometer

we shouldn't use <array>.extend([<generator>]) it's similiar to
<array>.extend(<generator>) but slower

Change-Id: Ic859e9a477f03b680e1ac0db1498261a3dc24997
Transform sample_cnt type to int

Duration is seconds from current time, and sample_cnt on
the basis of duration. So sample_cnt always not a int, but
we need sample_cnt as a int type.

Closes-Bug:#1330330

Change-Id: I89e1768523384e24c3a0b8b76f4fa04a123248f9
Remove redundant parentheses

Ceilometer code contained redundant parentheses usages,
so they were removed.

Change-Id: I00cbb255a598984e33faade2c59865d926000733
Add keystone control exchange

This patch adds
1) Notification exchange for keystone
2) Abbility to profile keystone

In future we are going to add as well keystone
audit notification pluging

Change-Id: I21f78698431ef9da9ddf5771a0594e5ab7f755a5
Merge "Transform sample_cnt type to int"
Merge "Remove redundant parentheses"
Merge "Add keystone control exchange"
Merge "Improve a bit performance of Ceilometer"