shared/shell: Disable argument count check if optarg are detected

shared/shell: Disable argument count check if optarg are detected

Command which start with optional arguments might be using optargs
format in which case checking argument count check does not work so
this disables it which shall make things btmgmt work:

[mgmt]# add-adv --help
Usage: add-adv [options] <instance_id>
Options:
	 -u, --uuid <uuid>         Service UUID
	 -d, --adv-data <data>     Advertising Data bytes
	 -s, --scan-rsp <data>     Scan Response Data bytes
	 -t, --timeout <timeout>   Timeout in seconds
	 -D, --duration <duration> Duration in seconds
	 -c, --connectable         "connectable" flag
	 -g, --general-discov      "general-discoverable" flag
	 -l, --limited-discov      "limited-discoverable" flag
	 -n, --scan-rsp-local-name "local-name" flag
	 -a, --scan-rsp-appearance "appearance" flag
	 -m, --managed-flags       "managed-flags" flag
	 -p, --tx-power            "tx-power" flag
e.g.:
	add-adv -u 180d -u 180f -d 080954657374204C45 1
[mgmt]# add-adv -u 180d -u 180f -d 080954657374204C45 1
Instance added: 1

Change-Id: I6588e8a904d669843c2da9a5c43365d16752afd7
Signed-off-by: Amit Purwar <amit.purwar@samsung.com>