bkctld-check-incs: Correct shellchek warnings

- SC2013: To read lines rather than words, pipe/redirect to a 'while
  read' loop.
- SC2086: Double quote to prevent globbing and word splitting.

CHANGELOG.md

@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+* bkctld-check-incs: Correct shellsheck warnings
+
 ### Deprecated
 
 ### Removed

lib/bkctld-check-incs

@@ -7,7 +7,7 @@
 set -u
 
 # shellcheck source=./includes
-LIBDIR="$(dirname $0)" && . "${LIBDIR}/includes"
+LIBDIR="$(dirname "$0")" && . "${LIBDIR}/includes"
 
 # default return value is 0 (succes)
 rc=0
@@ -22,12 +22,12 @@ for jail_name in $("${LIBDIR}/bkctld-list"); do
 
     if [ -n "${incs_policy_file}" ]; then
         # get jail last configuration date
-        jail_config_epoch=$(date --date "$(stat -c %y ${incs_policy_file})" +"%s")
+        jail_config_epoch=$(date --date "$(stat -c %y "${incs_policy_file}")" +"%s")
 
-        # loop for each line in jail configuration
-        for line in $(cat ${incs_policy_file}); do
+        # read each line in jail configuration
+        while IFS= read -r line < "${incs_policy_file}"; do
             # inc date in ISO format
-            inc_iso=$(relative_date ${line})
+            inc_iso=$(relative_date "${line}")
             # inc date in seconds from epoch
             inc_epoch=$(date --date "${inc_iso}" +"%s")