Shell variables do not work correctly if a user parameter is defined without parameters.

As an example, suppose we have the following user parameters defined:

UserParameter=random.number1,echo $$RANDOM
UserParameter=random.number2[*],echo $$RANDOM

Using zabbix_get, we obtain incorrect values for random.number1:

$ ../bin/zabbix_get -s 127.0.0.1 -k random.number1
7994RANDOM
$ ../bin/zabbix_get -s 127.0.0.1 -k random.number1
7996RANDOM
$ ../bin/zabbix_get -s 127.0.0.1 -k random.number1
7998RANDOM

However, item random.number2 gives correct values:

$ ../bin/zabbix_get -s 127.0.0.1 -k random.number2
31836
$ ../bin/zabbix_get -s 127.0.0.1 -k random.number2
4928
$ ../bin/zabbix_get -s 127.0.0.1 -k random.number2
16573