also insert current value when discovering a sensor to get rid of NaN before first poll

git-svn-id: http://observium.org/svn/observer/trunk@4416 61d68cd4-352d-0410-923a-c4978735b2b8
SECURITY UPDATE: escape user-supplied parameters (eg. ipmi credentials, snmp credentials) before executing

git-svn-id: http://observium.org/svn/observer/trunk@4417 61d68cd4-352d-0410-923a-c4978735b2b8