Convert hostname to lower case to meet K8 naming constraints

[phariharan-wish-zz]

Issue

Hostname with upper case alphanumeric characters will fail the K8 naming validation

Invalid value: "merchant-oneoff-pod-Priyanka-local": a DNS-1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name', or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')

Fix

Convert hostname to lower case on login, up, down, and cp.

[codecov]

Codecov Report

Merging #40 into master will decrease coverage by 0.06%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #40      +/-   ##
==========================================
- Coverage   33.04%   32.98%   -0.07%     
==========================================
  Files          52       52              
  Lines        2082     2086       +4     
==========================================
  Hits          688      688              
- Misses       1366     1370       +4     
  Partials       28       28              

Impacted Files	Coverage Δ
cmd/cp.go	0.00% <0.00%> (ø)
cmd/down.go	0.00% <0.00%> (ø)
cmd/login.go	0.00% <0.00%> (ø)
cmd/up.go	0.00% <0.00%> (ø)

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