Merge "init: document what host init verifier checks"

    kill -SIGCONT 4343

    > strace runs

Host Init Script Verification

-----------------------------

Init scripts are checked for correctness during build time. Specifically the below is checked.

1) Well formatted action, service and import sections, e.g. no actions without a preceding 'on'

line, and no extraneous lines after an 'import' statement.

2) All commands map to a valid keyword and the argument count is within the correct range.

3) All service options are valid. This is stricter than how commands are checked as the service

options' arguments are fully parsed, e.g. UIDs and GIDs must resolve.

There are other parts of init scripts that are only parsed at runtime and therefore not checked

during build time, among them are the below.

1) The validity of the arguments of commands, e.g. no checking if file paths actually exist, if

SELinux would permit the operation, or if the UIDs and GIDs resolve.

2) No checking if a service exists or has a valid SELinux domain defined

3) No checking if a service has not been previously defined in a different init script.