[Lockfile](https://pypi.org/project/lockfile/) has not been maintained
since around 2015. Further, the functionality it provided seems poor - a
review of the code indicated that it used the presence of the PID file
itself as the lock - in Unix, using a file's existence followed by a
creation is not atomic, so a lock could be prone to race conditions.

The lockfile package also did not clean up after itself - a process
which was destroyed unexpectedly would not clear the created locks, so
some faulty logic was added to mainUtils.py, which checked to see if a
process with the same PID as the lockfile's creator was running. This
is obviously failure prone, as a new process might be assigned the same
PID as the old lockfile's owner, without actually being the same process.

(Of note, the SIG_DFL argument to os.kill() is not a signal at all, but
rather of type signal.handler. It appears that the python cast this
handler to the int 0, which, according to man 2 kill, leads to no signal
being sent, but existance and permission checks are still performed. So
it is a happy accident that this code worked at all)

This commit removes lockfile from the codebase entirely.

It also adds a "PIDLockFile" class which provides an atomic-guarenteed
lock via the mkdir and rmdir commands on Unix - thus, it is not safely
portable to Windows, but this should not be an issue as only Unix-based
utilities use the "simple_main()" function.

PIDLockFile provides API compatible classes to replace most of the
functionality from lockfile.PidLockFile, but does remove any timeout
logic as it was not used in any meaningful sense - a hard-coded timeout
of 1 second was used, but an immediate result of if the lock is held is
sufficient.

PIDLockFile also includes appropriate __enter__, __exit__, and __del__
attributes, so that, should we extend this class in the future, with
syntax is functional, and __del__ calls release, so a process reaped
unexpectedly should still clean its own locks as part of the garbage
collection process.
Authored-by: NTyler Ramer <tramer@pivotal.io>