pki: Search OpenSSH header not only at the beginning
Try to find the OpenSSH private key header not only at the beginning of
the file. This makes the parser to skip comments and white spaces.
Signed-off-by: Anderson Toshiyuki Sasaki <firstname.lastname@example.org>
Reviewed-by: Andreas Schneider <email@example.com>
(cherry picked from commit 88d777e6782330be8d6916f672ae106a5bd32b10)