Functional test: Fix pretty print
Functional test: Fix pretty print

As pretty printing of differences occurs only if the strings are
different, `git diff` will never return `0`.
Nevertheless, `0` was expected, resulting in a warning about being
unable to pretty-print the differences.

Fix by testing for `1`, using `WEXITSTATUS` to
retrieve the `git diff` return code on POSIX platforms.

Signed-off-by: Kevin Rocard <f6672397850e914591889d29dcaf9077eb1a8a4f@intel.com>

miguelgaio/parameter-framework,mgaio/parameter-framework,01org/parameter-framework,dawagner/parameter-framework,krocard/parameter-framework,clero/parameter-framework,dawagner/parameter-framework,dawagner/parameter-framework,krocard/parameter-framework,01org/parameter-framework,mgaio/parameter-framework,miguelgaio/parameter-framework,01org/parameter-framework,krocard/parameter-framework,mgaio/parameter-framework,clero/parameter-framework,miguelgaio/parameter-framework,clero/parameter-framework