self-diagnostics: substitute possible slashes in report names
Certain device models have slashes in their names, causing self-diagnostics to fail:
root@board-abcdef123456:~# self-diagnostics -j
tar: can't open '/tmp/self-diagnostics-report-Some_Board_Alpha/Bravo-0123456789.tar': No such file or directory
gzip: /tmp/self-diagnostics-report-Some_Board_Alpha/Bravo-0123456789.tar: No such file or directory
{ "result": "\/tmp\/self-diagnostics-report-Some_Board_Alpha\/Bravo-0123456789.tar.gz" }
Slashes aren't valid in filenames, therefore should be removed/replaed.
Substitute forward slashes with underscores.
Additionally, clean up trailing tabs in self-diagnostics package.