Werk #13912: Fix crash on restarting the RRDHelper

The RRDHelper may need to be restarted without a full restart of the CMC. This could lead to an internal error and crash the CMC as well with a traceback such as

/omd/sites/.../bin/cmc(_Z11sig_survivei+0xc2) [0x6656d2] /lib/x86_64-linux-gnu/libc.so.6(+0x42520) [0x7fca01440520] /lib/x86_64-linux-gnu/libc.so.6(pthread_kill+0x12c) [0x7fca01494a7c] /lib/x86_64-linux-gnu/libc.so.6(raise+0x16) [0x7fca01440476] /lib/x86_64-linux-gnu/libc.so.6(abort+0xd3) [0x7fca014267f3] /omd/sites/.../bin/cmc() [0x64e6a5] /omd/sites/.../bin/cmc(_ZN10__cxxabiv111__terminateEPFvvE+0xa) [0xa0e61a] /omd/sites/.../bin/cmc() [0xa0e685] /omd/sites/.../bin/cmc(_ZN16DataExportThreadIN9rrdcached8protocol6UpdateENS1_6ReloadEE5startEv+0x78) [0x755998] /omd/sites/.../bin/cmc(_ZN9RRDHelper6createEPK6Object9RRDFormatRKSt6vectorI6MetricSaIS5_EE+0x703) [0x74ef33] /omd/sites/.../bin/cmc(_ZN9RRDHelper13processSingleERK15PerformanceDataPK6ObjectRK7RRDInfo+0xab0) [0x753780] /omd/sites/.../bin/cmc(_ZN9RRDHelper15processPerfDataERK15PerformanceDataPK6Object+0xdd) [0x75452d] /omd/sites/.../bin/cmc(_ZN4Core15processPerfdataEPK6Object+0xa1) [0x66b4b1] /omd/sites/.../bin/cmc(_ZN4Core25objectStateHasBeenChangedEP6Object+0x1c0) [0x66c370] /omd/sites/.../bin/cmc(_ZN4Core18processCheckResultERK11CheckResult+0x91) [0x66c801] /omd/sites/.../bin/cmc(_ZN11CheckHelper9getResultEv+0xb69) [0x8698e9] /omd/sites/.../bin/cmc(_ZN11CheckHelper12communicate_ERK6Poller+0xe6) [0x869c66] /omd/sites/.../bin/cmc(_ZN15CheckHelperPool12communicate_ERK6Poller+0x45) [0x86b5f5] /omd/sites/.../bin/cmc(_ZN4Core8mainLoopEv+0x4f5) [0x6724e5] /omd/sites/.../bin/cmc(_ZN4Core3runEv+0xae5) [0x673415] /omd/sites/.../bin/cmc(main+0xf1f) [0x65410f] /lib/x86_64-linux-gnu/libc.so.6(+0x29d90) [0x7fca01427d90] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x80) [0x7fca01427e40] /omd/sites/.../bin/cmc(_start+0x25) [0x65b675]

To the list of all Werks