memcached -l argument generates server error

To increase the connection limit for port 11209 it is necessary to override the -l argument passed from ns-server to memcached, either via a wrapper script or via the diag/eval endpoint. In 3.0 this now generates an "Unexpected Server error". The -c flag for overall connection limit works as expected.

Steps to reproduce:

Running:

curl --data 'ns_config:set({node, node(), {memcached, extra_args}}, ['-l0.0.0.0:11210,0.0.0.0:11209:3000']).' -u Administrator:<PASSWORD> http://localhost:8091/diag/eval

Will generate an "Unexpected Server error" on 3.0.x but will return OK in 2.5.x