target: Fix incorrect strlen() NULL terminator checks

This patch fixes a number of cases in target core using an incorrectly

	if (strlen(foo) > SOME_MAX_SIZE)

As strlen() returns the number of characters in the string not counting
the NULL character at the end.  So if you do something like:

        char buf[10];

        if (strlen("0123456789") > 10)
                return -ETOOLONG;
        snprintf(buf, 10, "0123456789");
        printf("%s\n", buf);

then the last "9" gets chopped off and only "012345678" is printed.

Plus I threw in one small related cleanup.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>