MDEV-7993 file_key_management_filekey doesn't work as expected with FILE:

chomp the secret, as read from the file. remove trailing
CR and LF bytes.

mysql-test/suite/encryption/t/filekeys-data.key

@@ -1 +1,2 @@
 secret
+

plugin/file_key_management/parser.cc

@@ -173,6 +173,7 @@ bool Parser::read_filekey(const char *filekey, char *secret)
   my_close(f, MYF(MY_WME));
   if (len <= 0)
     return 1;
+  while (secret[len - 1] == '\r' || secret[len - 1] == '\n') len--;
   secret[len]= '\0';
   return 0;
 }