We document that this can be disabled by setting the
[pxe]tftp_master_path config to "<None>", but don't
actually support it in code. oslo.config doesn't actually
translate that value to the Python None as we expect.
Allow disabling the cache by setting the config to the empty
string, as in "tftp_master_path=". This doesn't make sense as
a directory to use as a cache anyway, so it shouldn't break anyone.
Conflicts:
ironic/common/pxe_utils.py
ironic/tests/unit/common/test_pxe_utils.py
Affected code is in ironic/drivers/modules/pxe.py and
ironic/tests/unit/drivers/modules/test_pxe.py. (They
got moved into pxe_utils in master branch).
Change-Id: Icc7d08ae47e0e450a612c922ae3d665c56880262
Story: 2004608
Task: 28506
(cherry picked from commit 4c987aa51b)
c0ed86db7c