diotest: use safe format argument to tst_resm()

Prior to this commit, the diotest4 test failed to build if
-Werror=format-security was used. The compiler could not examine the
contents of the msg variable.

Adjust the tst_resm calls so that the format string is a string literal.

Fedora recently enabled this compiler option in their RPM builds, so
this fixes the build on Fedora 21.

Signed-off-by: Ken Dreyer <kdreyer@redhat.com>
1 file changed