Fix Shellcheck warnings found with coverity scan

Author: IzabelaBakollari

common/python_wrapper.sh

@@ -1,7 +1,6 @@
 #! /bin/sh
-EXEC_PATH=`readlink -f $0`
-EXEC_NAME=`basename $EXEC_PATH`
-EXEC_DIR=`dirname $EXEC_PATH`
+EXEC_PATH=$(readlink -f "$0")
+EXEC_NAME=$(basename "$EXEC_PATH")
 
 mlibdir=@MST_LIB_DIR@
 #@POST_MST_LIB_DIR@  # Update the lib dir by the post install script.
@@ -10,7 +9,7 @@ mbindir=@MST_BIN_DIR@
 
 MSTFLINT_EXT_PYTHON_LIB_DIR=$mlibdir/mstflint/python_ext_libs
 MSTFLINT_PYTHON_TOOLS=$mlibdir/mstflint/python_tools
-PY_TOOLS_REL_PATHS=$(dirname $0)/../lib/mstflint/python_tools:$(dirname $0)/../lib64/mstflint/python_tools
+PY_TOOLS_REL_PATHS=$(dirname "$0")/../lib/mstflint/python_tools:$(dirname "$0")/../lib64/mstflint/python_tools
 
 if test -z "${PYTHONPATH}"; then
    PYTHONPATH=$MSTFLINT_PYTHON_TOOLS:$PY_TOOLS_REL_PATHS:$MSTFLINT_EXT_PYTHON_LIB_DIR
@@ -22,7 +21,7 @@ export PYTHONPATH
 export MSTFLINT_LIB_DIR=$mlibdir
 export LD_LIBRARY_PATH=$mlibdir
 export MSTFLINT_BIN_DIR=$mbindir
-PYTHON_EXEC=`find /usr/bin /bin/ /usr/local/bin -iname 'python*' 2>&1 | grep -e='*python[0-9,.]*' | sort -d | head -n 1`
+PYTHON_EXEC=$(find /usr/bin /bin/ /usr/local/bin -iname 'python*' 2>&1 | grep -e='*python[0-9,.]*' | sort -d | head -n 1)
 which python3 >/dev/null 2>&1
 if test $? -eq 0 ; then
    PYTHON_EXEC='/usr/bin/env python3'
@@ -35,8 +34,8 @@ fi
 
 SCRIPT_PATH=$MSTFLINT_PYTHON_TOOLS/${EXEC_NAME}/${EXEC_NAME}.py
 
-if test ! -f $SCRIPT_PATH; then
-    SCRIPT_PATH=$(find $MSTFLINT_PYTHON_TOOLS $(echo $PY_TOOLS_REL_PATHS | sed "s/:/ /g")  -name ${EXEC_NAME}.py 2>/dev/null | head -n 1)
+if test ! -f "$SCRIPT_PATH"; then
+    SCRIPT_PATH=$(find "$MSTFLINT_PYTHON_TOOLS" "$(echo "$PY_TOOLS_REL_PATHS" | sed "s/:/ /g")"  -name "${EXEC_NAME}.py" 2>/dev/null | head -n 1)
 fi
 
 if test -z "${SCRIPT_PATH=}"; then