Support different publisher interval

Changes the agent manager to poll based on pipeline configuration, to
support different interval requirement from different publishers.

This patch clean up the test case for agent managers. It makes the changes
a bit bigger, however, it's not so easy to seprate this cleanup patch
with different interval part.

For bp publisher-counters-frequency

Change-Id: I3c1163e37de6a17261d2c570843845696ebff58f
Signed-off-by: Yunhong, Jiang <yunhong.jiang@intel.com>
Simplify PollingTask building

Change-Id: I142c2b6b46fed3458b1d0c74c7ba7a190dbe6e00
Signed-off-by: Julien Danjou <julien@danjou.info>