Use "command -v" instead of "which" to find path
Use "command -v" instead of "which" to find path

If /usr/bin/which is not available, the current code
doesn't detect i.e. /usr/bin/zypper . Using "command -v" solved
the problem.

Change-Id: I1c281c3184d69cd9dc2418295b6a392d8e5693e0

dirkmueller/devstack,dirkmueller/devstack