powerman: support new setresult directive

[chu11]

Problem: In many cases, there is no way for a power operation (i.e. power on, but not power status) to inform powerman that an error has occurred in the operation. The user will always get a "Command completed successfully" output and exit status 0 after issuing a power operation.

Solution: Support a new "setresult" statement that can inform powerman that a power operation did not succeed. A regex can be used to determine what output is expected of a successful power operation. If any are not successful, powerman can subsequently inform the user an error has occurred, leading to a "Command completed with errors" message and exit status 1.

Some example uses:

script on_all {
    send "on\n"
    foreachnode {
        expect "([^\n:]+): ([^\n]+\n)"
        setresult $1 $2 success="^ok\n"
    }
    expect "redfishpower> "
}

script on {
    send "on %s\n"
    expect "([^\n:]+): ([^\n]+\n)"
    setresult $1 $2 success="^ok\n"
    expect "redfishpower> "
}

[chu11]

i'm going to close this as I've recently merged this into my mega cray ex chassis PR chain. Don't want to mess up the order of all the broken up PRs.