patch 9.1.1122: too many strlen() calls in findfile.c

Problem:  too many strlen() calls in findfile.c
Solution: refactor findfile.c and remove calls to strlen()
          (John Marriott)

closes: #16595

Signed-off-by: John Marriott <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: John Marriott