Problem: the test/tpm script has no users.

Drop script.

Problem: vpcd is a test program but it is installed.

Don't install it or its device script.

Problem: the test suite sets TEST_ETC in the test environment
but nothing uses it.

Drop TEST_ETC from the test environment.

Problem: the argv unit test lives in the test subdirectory
with a custom driver.

Move it to the libcommon directory, near the source it is testing.
Have 'make check' run it directly.

Problem: pluglist class is only used by powerman yet it
resides in libcommon.

Move pluglist to the powerman directory.
Move the pluglist unit test to the powerman directory, but
leave its driver in the top test directory for now.

Problem: the xregex unit test lives in the test subdirectory
with a custom driver.

Move it to the libcommon directory, near the source it is testing.
Have 'make check' run it directly.

Problem: the API client test program lives in the top level
test directory, but it would be usefully co-located with the
source code that it tests.

Move test/cli.c to src/powerman/test/apiclient.c.
Update test driver in the top level test directory.

Problem: unit testing is required for some small classes
used in powerman.

Pull in libtap (via the flux-pmix project), originally from
https://github.com/zorgnax/libtap

Problem: TAP output is not interpreted by 'make check'.

Prepare to add TAP tests by adding the automake TAP driver.

Problem: argv unit test just asserts on failure.

Convert it to a libtap unit test and run it with the TAP driver.
Rename executable with .t suffix to indicate that it's a TAP test.

Problem: xregex unit test just asserts on failure.

Convert it to a libtap unit test and run it with the TAP driver.
Rename executable with .t suffix to indicate that it's a TAP test.