testutil/integration: sundry changes to improve usability and robustness
1. do not start a root mount table as a module by default. The intent
of this framework is to test binaries and their command lines, so we
should build a mount table and run it as binary rather than as a module
(which is really a library linked into the same address space as the test).
2. maintain a LIFO ordered list of current invocations and kill them
in that order on cleanup.
3. create an expect.Session for each invocation since many callers will
do this directly.
4. add a list of TODOs for improvements that are required in the near
term.
5. update mounttabled, proxyd to print their names to stdout so that
integration tests don't have to read stderr and logs to obtain that
info.
Change-Id: I7724d09e1d65cca79adf9722992c515cb61bd80f
10 files changed
