Fix boolean values when checking array

[kubaw]

I think checking condition like this: rvm1_rubies | bool doesn't work for array. It is always false.
This causes an error:

"stderr": "/bin/sh: /home/user/.rvm/wrappers//gem: not found"

Looks like checking using | length works for arrays but it is also works for strings.

[pkuczynski]

@kubaw thank you for your contribution and apologies for the late merge. I will invite you to the RVM team so you can have better influence on this package...

[thbar]

@rvm/ansible I have tested this PR successfully on a client deployment.

Not only the warnings disappears, but #209 also appears to be closed (I'll comment over there).

Logs before:

TASK [rvm.ruby : Detect if rubies are installed] ************************************************************
[DEPRECATION WARNING]: evaluating ['ruby-2.5.8', 'ruby-2.5.7', 'ruby-2.5.3'] as a bare variable, this 
behaviour will go away and you might need to add |bool to the expression in the future. Also see 
CONDITIONAL_BARE_VARS configuration toggle.. This feature will be removed in version 2.12. Deprecation 
warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.
skipping: [vagrant-xyz] => (item=ruby-2.5.8) 
skipping: [vagrant-xyz] => (item=ruby-2.5.7) 
skipping: [vagrant-xyz] => (item=ruby-2.5.3) 

Logs after:

TASK [rvm.ruby : Detect if rubies are installed] ************************************************************
skipping: [vagrant-xyz] => (item=ruby-2.5.8) 
skipping: [vagrant-xyz] => (item=ruby-2.5.7) 
skipping: [vagrant-xyz] => (item=ruby-2.5.3) 

Thanks @kubaw!