Please verify whether the line 1576 in /usr/share/perl5/PVE/DAB.pm (in dab v1.1.9) is valid.
It currently states:
my $rpw = $password eq 'random' ? 'admin' : $password;
<del>This is possibly wrongly inverted</del>.
It appears that a script is inited - mysql_randompw - so that it is generated to be a 9 character random string at creation time of container.
At line 26 of the /etc/init.d/mysql_randompw , the mysqladmin statement is invoked - at this stage in the DAB.pm at line 1585 where it is called from. Only subsequently in DAB.pm at line 1589 is the mysql started.