Use format strings directly to prevent -Werror=format-security failures

Use format strings directly to prevent -Werror=format-security failures

Gcc is too stupid to realize that:

    const char *usage="String which has no percent signs";

    com_err(progname, 0, usage);

is OK.  I refuse to bow to stupidity with:

   com_err(progname, 0, "%s", usage);

but I will use the string directly for the sake of people who like to
build with -Werror=format-security.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>