docker: fix r path in doker_init.sh

src/.docker_modules/r-base/3.5.3/docker_init.sh

 #!/bin/sh
 docker pull lbmc/r:3.5.3
-docker build src/.docker_modules/r/3.5.3 -t 'lbmc/r:3.5.3'
+docker build src/.docker_modules/r-base/3.5.3 -t 'lbmc/r:3.5.3'
 docker push lbmc/r:3.5.3

src/.docker_modules/r-base/3.6.2/docker_init.sh

 #!/bin/sh
 docker pull lbmc/r-base:3.6.2
-docker build src/.docker_modules/r/3.6.2 -t 'lbmc/r-base:3.6.2'
+docker build src/.docker_modules/r-base/3.6.2 -t 'lbmc/r-base:3.6.2'
 docker push lbmc/r-base:3.6.2

src/.docker_modules/r-base/4.0.0/docker_init.sh

 #!/bin/sh
 docker pull lbmc/r-base:4.0.0
-docker build src/.docker_modules/r/4.0.0 -t 'lbmc/r-base:4.0.0'
+docker build src/.docker_modules/r-base/4.0.0 -t 'lbmc/r-base:4.0.0'
 docker push lbmc/r-base:4.0.0