regfile: Fix regular file open and lseek on restore

1. Seeking should be done for real files only , for fifos using the
   same code -- shouldn't. Thus -- move the lseek to proper place;
2. It's nice to print error on file open error;
3. It's nice to handle lseek error.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>