app/test: disable filtering with stripped binary

The unavailable tests are filtered out by autotest by looking for
the symbols in the binary:

PCI autotest:                  Skipped [Not Available]       [00m 00s]
Malloc autotest:               Success                       [00m 00s]

It results to skip everything if the binary has no symbol (stripped):

PCI autotest:                  Skipped [Not Available]       [00m 00s]
Malloc autotest:               Skipped [Not Available]       [00m 00s]

This case is handled by getting back to the old behaviour if the binary
has no symbol information:

PCI autotest:                  Fail [Not found]              [00m 00s]
Malloc autotest:               Success                       [00m 00s]

Fixes: d553c8f2b1a2 ("app/test: filter out unavailable tests")

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Tested-by: Olivier Matz <olivier.matz@6wind.com>