Fix spurious error from sysrc

When using sysrc to modify a file, the file should be created silently.
However, with the introduction of SVN r335280, an error of "No such file
or directory" would appear despite everything else working as-expected.

The nature of this spurious error is that SVN r335280 did not check if
the file exists first, before trying to fixup the line-endings in the
file just prior to modification.

PR: bin/240875
Reported by: Jose Luis Duran
MFC after: 3 days

(cherry picked from commit e19a2226fe3bbeeb6e922987475300868374d09a)