Fix syntax error in "drill-config.sh"
The drill-config.sh has a syntax error on line 144 with the usage of "let". The command following let should be enclosed in quotes, otherwise the following syntax error occurs:
/home/someone/proj/apache-drill-1.17.0/bin/drill-config.sh: line 144: let: lineCount=: syntax error: operand expected (error token is "=")
