Fix #15592: application error 0 in adm_config_report.php

This was due to a missing type cast in call to check_selected(). The
for loop was replaced by a call to print_option_list_from_array(), to
avoid code duplication.
adm_config_report.php: don't post filter data on config rows buttons

This is handled through cookie
adm_config_report: whitespace, coding guidelines
Config report: retrieval of saved project filter does not work

When retrieving a saved filter from the cookie in adm_config_report.php
the saved project id is not reflected in the filter's selection list:
'All Projects' is always selected instead of the actual project. This
value should only be picked as default when the project id does not
exist.

This is due to a missing negation in the check for project's existence.

Fixes  #15691
LOG_DATABASE causes 'Array to string conversion' system notice

This is due to using $p_msg instead of $s_msg in log_event() at line 93.

Fixes #15685