Set both ISC_PASSWD and ISC_PASSWORD to make both environment and old scripts happy

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58845 65644016-39b1-43b1-bf79-96bc8fe82c15
Fixed CORE-4283: Resource temporarily unavailable errors while simultaneously registering events

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58846 65644016-39b1-43b1-bf79-96bc8fe82c15
Fixed regression in unistaller which arrived when adding systemd support

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58848 65644016-39b1-43b1-bf79-96bc8fe82c15