ipsec: Only set PATH if it is not already set

The comment indicated this but it was always set anyway.  All internal
commands are called via their absolute paths, so the script only uses PATH for
the uname command, but if that is not located in one of the configured
directories the script will fail.

Also, since the internal commands are called via their absolute paths there is
no need to add the directories to PATH.

src/ipsec/_ipsec.in

@@ -15,7 +15,7 @@
 # for more details.
 
 # define a minimum PATH environment in case it is not set
-PATH="/sbin:/bin:/usr/sbin:/usr/bin:@IPSEC_SBINDIR@:@IPSEC_BINDIR@"
+PATH=${PATH:-"/sbin:/bin:/usr/sbin:/usr/bin"}
 export PATH
 
 # set daemon name