Deprecate num-instances in favor of min/max count

For 'nova boot', num_instances only set max_count, which will try to
launch up to max_count instances. But sometimes users want to either
launch min_count instances or nothing. So deprecate --num-instances
and use --min-count and --max-count instead.

DocImpact: deprecate '--num-instances' for 'nova boot'

Change-Id: If0088aef554a528258799b22c6e793541474cb0d
Closes-bug: #1309244
Remove duplicate test test_boot_multiple

test_boot_multiple is a duplicate if test_boot_num_instances.

Change-Id: I03a4def85b79109e6a950587542b53741b06bd70
Allow the default value of 1 to  be set for boot multiple

Allow one to call the following with their default values of 1:
* nova boot --num-instances 1
* nova boot --min-count 1
* nova boot --max-count 1

Don't allow min_count>max_count.

This is the only place where if a user passes in the default value the
CLI will return an error.

Change-Id: I805b3f0c778e9c70c5817624fb696a746dfe3d5b
Merge "Deprecate num-instances in favor of min/max count"
Merge "Remove duplicate test test_boot_multiple"
Merge "Allow the default value of 1 to  be set for boot multiple"