BUG/MINOR: tools: Fix loop condition in dump_text()

BUG/MINOR: tools: Fix loop condition in dump_text()

The condition should first check whether `bsize` is reached, before
dereferencing the offset. Even if this always works fine, due to the
string being null-terminated, this certainly looks odd.

Found using GitHub's CodeQL scan.

This bug traces back to at least 97c2ae13bc0d7961a348102d6719fbcaf34d46d5
(1.7.0+) and this patch should be backported accordingly.

(cherry picked from commit 18795d48a9bb09aedc57e547029828a56322e49d)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit cd5521e7ca7472bf69874603c0c5785d4ff1d1e2)
Signed-off-by: Willy Tarreau <w@1wt.eu>