Bug 23250: Just use an @ in the password

Bug 23250: Just use an @ in the password

Rather than try to use -y and symbols, since
older versions of pwgen don't have the -y,
Purposefully just shorten the generated
password to 15 characters and put @ on the end.
This avoids nasty shell globbing, fixes the
MySQL requiring a symbol by default in the
newer versions.

While @ at the end is less secure, the
password portion providing security is
still 15 characters long.

Before patch, password should have potentially
multiple ugly symbols in it.
After patch, when creating an instance, the
password will have an @ at the end of it.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 6a6866afa343e3b53ad77a36552e19404ac7afab)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>