run-*d.sh: support $SHELL values other than bash

run-*d.sh: support $SHELL values other than bash

Continuing the saga of --shell support we follow up the last
episode 7a042223 with support for --shell when $SHELL is something
other than bash.

Only the bash shell allows the "-l -i" combination.  It's an error
for other shells.  While the tcsh shell does allow "-l", it must
be given alone.  The other shells do not have a "login shell" option.
Instead they activate a login shell if the first character of arg 0
is a '-'.  All shells support the POSIX "-i" option though.

Support $SHELL when it's set to something other than bash by only
passing the "-i" option and make it a login shell by forcing arg 0
to start with a '-'.