pjproject_bundled: Compile pjsua with max log level = 2

pjproject_bundled:  Compile pjsua with max log level = 2

A while back, we changed config_site.h to set PJ_LOG_MAX_LEVEL = 6.
This allowed us to control the log level better from inside Asterisk.
An unfortunate side effect of this was that the pjsua binary and
python bindings were also compiled with log level set to 6 so whenever
a testsuite test that uses pjsua runs, it spits out 6795 lines of
debug in an instant even before the test starts.  I believe this
overruns the Jenkins capture buffer and prevents the test from
properly terminating.  In turn, this results in the testsuite just
hanging until the job is killed.  It's more frequent on the higher
end agents because they can spit out the messages faster.

Unfortunately, the messages are all spit out before we have control
of the python pj.Lib instance where we can set logging levels so the
only alternative was to actually compile pjsua and _pjsua.so with an
overridden PJ_LOG_MAX_LEVEL.  Although defining a lower max level was
done in the Makefile, the define in config_site.h had to be wrapped
with "#ifndef" so the change would take effect.

Change-Id: I2af9e7d48dde1927279c586c9c725d868fe6f3ff
(cherry picked from commit d7e5a747c312de18647213359103ce6022776864)