LA: fix initialization of PETSc KSP #238

Job	Run time
Setup - Linux	11s
Windows (MSVC) - MPI OFF - Debug OFF	7m 3s
Windows (MSVC) - MPI ON - Debug OFF	10m 46s
Windows (MSVC) - MPI OFF - Debug ON	3m 51s
Windows (MSVC) - MPI ON - Debug ON	4m 53s
Linux (gcc) - MPI ON - Debug ON	19m 43s
Linux (gcc) - MPI ON - Debug OFF	6m 16s
Linux (gcc) - MPI OFF - Debug ON	11m 48s
Linux (gcc) - MPI OFF - Debug OFF	6m 6s
Linux (clang) - MPI ON - Debug OFF	5m 59s
	1h 16m 36s

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