Capomastro http check is broken

Capomastro http check is failing with:
Invalid HTTP response received from host: HTTP/1.1 400 BAD REQUEST

It's due to missing host header and bad regex in the check. Currently it's:
/usr/lib/nagios/plugins/check_http -I <IP> -p 80 -u / -e '302 FOUND' -u / -d 'http://capomastro/accounts/login/'

It should be:
/usr/lib/nagios/plugins/check_http -I <IP> -p 80 -H capomastro.canonical.com -u / -e '302 FOUND' -u / -d
'http://capomastro.canonical.com/accounts/login/'

Parameters are hardcoded in the charm so charm needs small patch and testing