SmartOS esky packaging: minor fixup

Don't assume that the top directory is named "salt"
The user might choose to name it "salt-<version>"
or "saltstack" or whatever else.

install.sh is already that flexible; this fixes _syspaths.py
Merge pull request #9927 from nshalman/smartos-esky-syspaths-fix

SmartOS esky packaging: minor fixup