Fix 198 to optimize fetching single functions

An optimization is introduced to the single replica reader which
means we use "Get" rather than "List" and filtering in memory.
I originally wrote the List/filter approach with the intention of
applying this change later. @imikushin from VMware suggested this
change and raised PR196 - since there were some issues with
process, Kubernetes version used and (lack of) testing I've
implemented the change and done testing for this.

[x] List functions gives correct content-type and list
[x] Individual function queries return the correct data and
content-type
[x] Individual function queries for non-existant functions give
404 when not found

Also tested through the OpenFaaS UI including testing that
there was no regression for the readiness feature.

Signed-off-by: Alex Ellis (VMware) <[email protected]>

Update filter methods and test for multiple removal

**What**
- Update the filter methods to filter instead of "pop" on the volume and
volumemount slices. This technique avoids allocations and possible index
errors that may occur from modifying the slice that we are iterating
over.
- Add a unit test to cover the case were a malformed deployment is
created that already contains more than one Volume and VolumeMount with
the secrets volume name.

**Why**
- This test ensures that we do not possibly introduce future bugs during
refactors.
- The methods needed to be refactored because the test found an
slice-indexing bug in the previous implementation.

Signed-off-by: Lucas Roesler <[email protected]>

Update Golang build SDK to 1.9.4

This was tested by Vivek Singh.

Signed-off-by: Alex Ellis (VMware) <[email protected]>

Enable port to be configured

The `port` env-var can now be set to configure the start-up TCP
port for faas-netes. This is required for when the daemon is run
inside a pod which already exposes port 8080.

Signed-off-by: Alex Ellis (VMware) <[email protected]>

Attempt to fix Docker CLI push issue

Update .travis.yml push behaviour

Updates bash push stage to use -z instead of -s check. Corrects
error in Travis build.

Attach SecretTypeDockerConfigJson secret type for deployments

The SecretTypeDockerConfigJson is now used as of Kubernetes 1.9
to store image pull secrets for fetching images from private
repositories. [0] This change allows SecretTypeDockerConfigJson
as a parallel option to the existing option SecretTypeDockercfg.

[0] https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/

Signed-off-by: Alex Ellis (VMware) <[email protected]>

Fix bad error messasge about updates to reads

Signed-off-by: Alex Ellis (VMware) [email protected] <[email protected]>

Code review: re-vendor and update to AvailableReplicas

Signed-off-by: Alex Ellis (VMware) <[email protected]>

Move to non-root user

Signed-off-by: Alex Ellis <[email protected]>