Fix for environment

https://forum.vestacp.com/viewtopic.php?t=11083

install/ubuntu/16.04/exim/exim4.conf.template

@@ -8,7 +8,10 @@
 #SPAM_SCORE = 50
 #CLAMD =  yes
 
+add_environment = <; PATH=/bin:/usr/bin
+keep_environment =
 disable_ipv6 = true
+
 domainlist local_domains = dsearch;/etc/exim4/domains/
 domainlist relay_to_domains = dsearch;/etc/exim4/domains/
 hostlist relay_from_hosts = 127.0.0.1