[SPARK-9249] [SPARKR] local variable assigned but may not be used

[[SPARK-9249] local variable assigned but may not be used - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-9249)

https://gist.github.com/yu-iskw/0e5b0253c11769457ea5

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #7640 from yu-iskw/SPARK-9249 and squashes the following commits:

7a51cab [Yu ISHIKAWA] [SPARK-9249][SparkR] local variable assigned but may not be used

R/pkg/R/deserialize.R

@@ -102,11 +102,11 @@ readList <- function(con) {
 
 readRaw <- function(con) {
   dataLen <- readInt(con)
-  data <- readBin(con, raw(), as.integer(dataLen), endian = "big")
+  readBin(con, raw(), as.integer(dataLen), endian = "big")
 }
 
 readRawLen <- function(con, dataLen) {
-  data <- readBin(con, raw(), as.integer(dataLen), endian = "big")
+  readBin(con, raw(), as.integer(dataLen), endian = "big")
 }
 
 readDeserialize <- function(con) {

R/pkg/R/sparkR.R

@@ -104,16 +104,13 @@ sparkR.init <- function(
     return(get(".sparkRjsc", envir = .sparkREnv))
   }
 
-  sparkMem <- Sys.getenv("SPARK_MEM", "1024m")
   jars <- suppressWarnings(normalizePath(as.character(sparkJars)))
 
   # Classpath separator is ";" on Windows
   # URI needs four /// as from http://stackoverflow.com/a/18522792
   if (.Platform$OS.type == "unix") {
-    collapseChar <- ":"
     uriSep <- "//"
   } else {
-    collapseChar <- ";"
     uriSep <- "////"
   }