encrypted passwords containing special characters appear to not work

Encrypted passwords which have a special character (such as $) appear to not work to auth to the backend servers.

To reproduce:

• use maxkeys to create maxscale keys
  maxkeys /var/lib/maxscale

• create maxscale database user with $ in the password
  grant all privileges on . to 'maxscale'@'localhost' identified by 'aaaaaaaaa$aaaaaaaaaa';

• use maxpasswd to generate encrypted version of password
  maxpassword /var/lib/maxscale aaaaaaaaa$aaaaaaaaaa

• use encrypted password in maxscale.cnf
  EED7D82309F2898C7BE84E389D8C70B1

• restart maxscale
  service maxscale start

• log into maxadmin and list servers, auth failed
  Auth Error, Down

• change maxscale database user password to not contain special characters
  set password for 'maxscale'@'localhost' = password('aaaaaaaaaaaaaaaaaaaa');

• use maxpasswd to generate encrypted version of password
  maxpasswd /var/lib/maxscale aaaaaaaaaaaaaaaaaaaa

• use encrypted password in maxscale.cnf
  059F56E071BFA3BFDA8FE4C832D8B7E94D2499B099C8BA3ADED096BB298239A1

• restart maxscale
  service mysql restart

• log into maxadmin and list servers, auth succeeded and all works
  Master, Running