[source] base-files: rc.common: fix enable() return code and logic

[LEDE Commits]

blogic pushed a commit to source.git, branch master:
https://git.lede-project.org/0b1fa809d0e974398503a24e408c1209969711f7

commit 0b1fa809d0e974398503a24e408c1209969711f7
Author: Roman Yeryomin <roman at advem.lv>
AuthorDate: Fri Dec 22 13:04:46 2017 +0200

    base-files: rc.common: fix enable() return code and logic
    
    In current state, if there is START but no STOP, enbale()
    will return 1 (failure), which is wrong.
    Moreover there is no need to check for START/STOP twice.
    Instead, add err variable to save success state and
    and return it's value.
    Also eliminate the need to disable() by using 'ln -sf',
    which will first delete the old symlink if one exists.
    
    Changes from v1:
    - fixed description
    
    Signed-off-by: Roman Yeryomin <roman at advem.lv>
---
 package/base-files/files/etc/rc.common | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/package/base-files/files/etc/rc.common b/package/base-files/files/etc/rc.common
index a2ea6a5..a08c1f8 100755
--- a/package/base-files/files/etc/rc.common
+++ b/package/base-files/files/etc/rc.common
@@ -41,14 +41,15 @@ disable() {
 }
 
 enable() {
+	err=1
 	name="$(basename "${initscript}")"
-	disable
-	[ -n "$START" -o -n "$STOP" ] || {
-		echo "/etc/init.d/$name does not have a START or STOP value"
-		return 1
-	}
-	[ "$START" ] && ln -s "../init.d/$name" "$IPKG_INSTROOT/etc/rc.d/S${START}${name##S[0-9][0-9]}"
-	[ "$STOP"  ] && ln -s "../init.d/$name" "$IPKG_INSTROOT/etc/rc.d/K${STOP}${name##K[0-9][0-9]}"
+	[ "$START" ] && \
+		ln -sf "../init.d/$name" "$IPKG_INSTROOT/etc/rc.d/S${START}${name##S[0-9][0-9]}" && \
+		err=0
+	[ "$STOP" ] && \
+		ln -sf "../init.d/$name" "$IPKG_INSTROOT/etc/rc.d/K${STOP}${name##K[0-9][0-9]}" && \
+		err=0
+	return $err
 }
 
 enabled() {