Report why a server call failed everywhere, not just at task completion

[mastacontrola]

Follow-on to #162, which fixed the blank * Error returned: at task completion. Every other script that talks to the FOG server still read res=$(curl -Lks --data ...), which collapses a connect failure, an HTTP error, an empty 2xx and a real answer into one empty string — so the same silence #162 fixed at completion was still there at check-in, registration, inventory, capone and the multicast capability probe.

What changed

postToServer is generalized to callServer <url> [data] — GET when no data is given, POST when there is, because it is the same exchange either way. It returns:

rc	meaning
0	a body came back
1	the call failed (transport, or HTTP >= 400)
2	answered 2xx with an empty body

Three outcomes rather than two, because a few endpoints answer empty on purpose and a caller has to be able to tell that from a dead server — which is exactly what fog.man.reg's location and OU prompts need.

23 call sites across 12 scripts converted.

Bugs found on the way

• fog.inventory printed Done after giving up. All eleven attempts could fail and the operator was told it worked.
• fog.capone reported Count not find (sic) and blamed the image for what may have been a transport failure.
• restoreLVMPartition's capability probe told the operator their server was too old to multicast LVM when the probe had never reached it — a claim about the server's version drawn from a dead network. Same shape as fogproject#1266.
• fog.man.reg's locationcheck/oucheck skipped their prompts silently on a failed GET, so a host registered into no location with nothing on screen to say so.
• fog.checkin and fog.man.reg looped without reporting anything at all.

Regression fixed from #162

res=$(curl ...) strips trailing newlines; the helper did not. A server whose reply ended in a newline yielded ##\n, every == "##" comparison failed, and a capture that had succeeded retried eleven times and then gave up. Case 5b pins it — and had to be written twice: the first cut read the body through head -1, which cannot see a trailing newline, and stayed green with the fix removed.

Left on raw curl deliberately

Each with its reason in a comment at the call site: fog.statusreporter (a 3s ping would paint over imaging output), fog.av (fire-and-forget), reportToServer (its contract is silence — pinned by tests/checks/error-report.sh), the secureboot-funcs.sh and bin/fog -o downloads, and S40network's connectivity probe.

Tests

tests/checks/server-post-reporting.sh → 15 assertions, adding the GET/POST split, the three return codes, and two whole-overlay sweeps: no call site may wrap callServer in $( ) (the subshell discards every variable it set — the bug this file exists to prevent), and raw curl may read a reply only in the exceptions listed above.

tests/checks/lvm.sh → case 30 for an unreachable capability probe, and its curl stub now emits the -w status line it always implied.

Every new assertion was mutation-verified red before being kept:

mutation	goes red
always send --data	9. GET path
empty body returns 1 not 2	3, 10
wrap a call site in $( )	11a
revert a site to raw curl	11b
revert the caps gate to $( )	lvm 30 (5 assertions)

Full suite: 15 check scripts pass, golden output byte-identical.