Fix the missing char when showing recovery logs.

This is a regression when adding support for margin space in commit
171b4c4c.

We're losing one char when showing long log lines. Because text_ is
aware of kMarginWidth, but not the the added indent (TEXT_INDENT).

Test: 'View recovery logs' on angler, with no missing character.
Change-Id: I284d54681d603e85e69d8e9c25173b1437a704df