testError format strings: explicitly include domain and network names

testError format strings: explicitly include domain and network names

This repairs the "make check" failure of tests/undefine.
* src/test.c (testResumeDomain, testPauseDomain): Likewise.
(testShutdownDomain, testGetDomainInfo, ): Likewise.
(testSetMemory, testSetVcpus, testDomainCreate, testDomainUndefine)
(testDomainGetSchedulerType, testDomainGetSchedulerParams): Likewise.
(testDomainSetSchedulerParams, testNetworkUndefine): Likewise.
(testNetworkStart, testNetworkGetBridgeName): Likewise.
(testDomainCoreDump, testDomainSave): Likewise, and...
Name the file upon failed open or write.
Use strerror(errno) in diagnostics.
* tests/undefine: Adjust expected output.

test.c (testError): Remove now-ignored dom and net parameters.
This is a sytnax-only change: removing the two unused parameters
and updating all callers:
* src/test.c (GET_DOMAIN, GET_NETWORK, testError)
(testBuildCapabilities, testOpenDefault, testOpenFromFile)
(testOpen, testGetHostname, testGetURI, testGetCapabilities)
(testLookupDomainByID, testLookupDomainByUUID)
(testLookupDomainByName, testResumeDomain, testPauseDomain)
(testShutdownDomain, testGetDomainInfo, testDomainSave)
(testDomainRestore, testDomainCoreDump, testGetOSType)
(testSetMemory, testSetVcpus, testListDefinedDomains)
(testNodeGetCellsFreeMemory, testDomainCreate)
(testDomainUndefine, testDomainGetSchedulerType)
(testDomainGetSchedulerParams, testDomainSetSchedulerParams)
(testLookupNetworkByUUID, testLookupNetworkByName)
(testListNetworks, testListDefinedNetworks, testNetworkUndefine)
(testNetworkStart, testNetworkGetBridgeName): Update callers.