Do not check if the local host is "alive"

The broctl cron and install commands check whether a host is "alive"
or not, but there is no need to do this check for the local host.
Checking the local host results in attempting to ssh to the local host,
which may (depending on ssh config and whether the graphical ssh-askpass
can run successfully) result in the user being prompted by ssh-askpass
to enter "yes" or "no" (for the host key verification).  This can happen
regardless of whether the user is running broctl interactively or just
running the broctl tests.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Do not check if the local host is "alive"
Add another warning message when a host is not alive

When a host is found to be not alive, a warning message is output (as
expected), but the warning is shown only the first time the check fails.
This is especially problematic for the broctl install command, because
it does not show any indication of a problem after the first such
unsuccessful run.

Added another warning message (worded slightly differently) to avoid
confusion in these situations.  For example, a user ran "broctl install"
twice, but only saw a warning the first time.  Next, running
"broctl start" resulted in a misleading error message that had nothing
to do with the actual problem.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Add another warning message when a host is not alive
Improve the check-pid helper script

Many of the broctl commands rely on the check-pid helper script, but it
was unreliable on OS X (most, if not all, of the recent test failures
seem to be caused by this) due to an excessive number of child
processes spawned in parallel (10 for each check-pid, for each Bro node).
As a result, occasionally the script would fail to identify a running
Bro process (it would return 1 instead of the expected value of 0).
Fixed by simplifying the script (reduced the number of child processes
by half), and it seems to be much more reliable.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Improve the check-pid helper script
Updating CHANGES and VERSION.
Updating version number in doc.
Merge remote-tracking branch 'origin/master' into topic/dnthayer/ticket845