Cleanup use of the bash "-x" flag

Removed the bash "-x" flag from all of the test files, and instead
use it only in the broctl-test-setup script used by all tests.
Improve the build and setup scripts for the broctl tests

Added a new Makefile target "rerun" that reruns any failed tests in
order to avoid having to run "btest -r" manually.  Added another
Makefile target "cleanall" that provides an easier way to remove
the broctl test build directory.

There was no way to specify additional flags to "configure" that are
needed to build Bro, without hand-editing the build script.  Fixed by
allowing a user to define BROCTL_TEST_BUILDARGS containing any needed
configure options.

If the "configure" script failed, then there was no way to run the
tests without manually removing the broctl test build directory and
rebuilding.  Fixed by always running the "configure" script instead
of only when the build directory doesn't exist.

Removed the broctl-path script so that the broctl tests can be run
without needing the broctl test build directory.

Running the test suite the first time takes a long time and consumes
hundreds of MBs of disk space before any tests are run (due to building
Bro), which can be a waste of resources if one just wants to quickly
run both the Bro and broctl test suites.  Fixed by allowing a user to
define BROCTL_TEST_USEBUILD which will use the Bro default build
directory (instead of a custom build directory for the broctl tests).

Remove the tar file containing the Bro install before doing the build
in order to avoid any chance of using an old tar file (when the current
build fails).

Remove the temporary bro install directory before doing a build in
order to avoid a previous "make install" failure causing the user to
have to manually remove that directory.

Added a few more error checks to the build script to better report
errors to the user.
Improve testing of broctl start and stop commands

Added several new tests (slow start of Bro, slow stop of Bro, starting
and stopping a large number of nodes on one host, restart with "--clean"
option).  Improved most of the existing tests by testing additional
aspects of the start and stop commands (such as sending crash reports,
logging to stats.log, and more test cases when a node crashes).

The "bro" test script now recognizes two new options in its config file:
"slowstart", and "slowstop".  These can be used to simulate a Bro
that is slow to initialize or that is slow to stop (i.e., cannot
be terminated with SIGTERM, so broctl must fallback to using SIGKILL).

Added a "sendmail" test script that can be used in place of the real
sendmail (the test script is faster and easier to test with).

Added a new function "replaceprefix" that any test can use.  It
replaces the text "@PREFIX@" in a test-specific file with the
test-specific Bro install prefix.

Added a new command-line option "--peers" to the diff-status-output
canonifier that indicates whether we want to include the "Peers" column
of the broctl status output in the diff (when we're not running the real
Bro, then the values in that column are not predictable or useful).
Update the broctl testing README
Improved diff canonifiers

Improved a couple diff canonifiers and added a few new ones in order
to do more thorough checking of test output.
Add tests of env_vars with myricom and pf_ring plugins

Added tests using the env_vars option (in broctl.cfg and node.cfg) to
add or override environment variables with the myricom and pf_ring plugins.
Add more tests of the broctl cron command
Improve error output

Improved some error messages in the test setup script and removed
another "-x" flag from bash in one of the tests.
Add more testing of sending crash reports
Merge remote-tracking branch 'origin/master' into topic/dnthayer/test-improvements
Add tests of the to-bytes.awk helper script

Also fixed some code formatting in to-bytes.awk so the code is easier
to read.
Add tests of the archive-log script

Added tests of the archive-log script, to verify that it archives
(with or without compression) a specified log file, and generates
a connection summary report if the conn.log file is being archived.
Add tests of the make-archive-name script

Also fixed some formatting in make-archive-name so the comments
are easier to read.
Add tests of various broctl options

Added tests of the following broctl options:  croncmd, sitepolicypath,
broargs, timefmt, makearchivename.
More thorough testing of broctl check and cleanup commands
More thorough testing of broctl install and cron commands
Improve testing of broctl scripts command

Also renamed some timestamp diff canonifiers to make the intended
usage more clear from the filename.
Add exit status tests of some broctl commands
Add tests of various broctl options
Miscellaneous small improvements to the test scripts

Also removed a baseline that is not needed.