src: fix compiler warnings

src: fix compiler warnings

Most of the fixes are printf format type warnings, but apparently GCC
6 is smart enough to realize is that if you don't do proper error
checking with posix_memalign, the resulting pointer can be undefined,
and whines about it.  So while fixing this in aio-dio-fcntl-race, I
also cleaned up the error checking and reporting.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>