Remove extra GetNewUnit calls from VTK.f90 #1189

Job	Run time
build-all-debug-single	3m 19s
build-postlib-release	10m 6s
build-all-debug	4m 41s
build-drivers-release	5m 2s
build-test-uadriver-debug	2m 4s
rtest-modules-debug	4m 36s
rtest-module-drivers	2m 28s
build-interfaces-release	3m 31s
build-openfast-release	3m 20s
build-fastfarm-release	10m 32s
rtest-OF-5MW_OC3Mnpl_DLL_WTurb_WavesIrr	3m 19s
rtest-OF-5MW_Land_BD_DLL_WTurb	2m 15s
rtest-OF-5MW_OC3Trpd_DLL_WSt_WavesReg	4m 35s
rtest-OF	6m 27s
rtest-OF-5MW_OC4Jckt_DLL_WTurb_WavesIrr_MGrowth	1m 0s
rtest-OF-5MW_OC4Semi_WSt_WavesWN	1m 30s
rtest-OF-linearization	3m 41s
rtest-interfaces	3m 10s
rtest-FF	2m 10s
	1h 17m 46s

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