Perfprofd: various changes related to config parameters.

Details:
- turn "max unprocessed profiles" into a configurable parameter.
- use a longer default collection interval
- reread config file on very iteration through the main loop,
  so as to incorporate new parameters written by the upload service

Bug: http://b/19483574
Change-Id: I1ecacbdeccf26f09ddd8387aef0f2587483eb967
(cherry picked from commit f353d8bf370eab2117e6259630f5540f12b361b0)
3 files changed