Option to configure pip source for murano-agent

With this small changes it becomes possible to instruct murano to
provision murano-agent of version other than latest, or from
custom git branch or from a http source.

Use cases:
* Use agent with custom modifications that are not available in
  PyPI version
* Development of new agent features - agent can be installed from
  the private git repo
* Environments without internet connectivity

Change-Id: Icbea95abf070ef35781474a54461cc34bb9927af

meta/io.murano/Classes/resources/LinuxMuranoInstance.yaml

@@ -93,6 +93,7 @@ Methods:
             "%MURANO_AGENT_CONF%": base64encode($muranoAgentConf)
             "%MURANO_AGENT_SERVICE%": base64encode($muranoAgentService)
             "%MURANO_AGENT%": base64encode($muranoAgent)
+            "%PIP_SOURCE%": config(engine, agent_source)
 
         - $userData: $muranoScript.replace($muranoReplacements) + $initScript.replace($scriptReplacements)
         - Return: $userData

meta/io.murano/Resources/murano-init.sh

@@ -17,7 +17,7 @@ else
   # TODO(kzaitsev): use deb/rpm packages as soon as we can
   echo "installing murano agent from pip"
   echo "binary not found in PATH: $PATH"
-  pip install murano-agent
+  pip install '%PIP_SOURCE%'
 fi
 
 muranoAgentConf='%MURANO_AGENT_CONF%'

murano/common/config.py

@@ -223,6 +223,9 @@ engine_opts = [
 
     cfg.StrOpt('signing_key', default='~/.ssh/id_rsa',
                help=_('Path to RSA key for agent message signing')),
+
+    cfg.StrOpt('agent_source', default='murano-agent',
+               help=_('pip URL/package spec for murano-agent')),
 ]
 
 # TODO(sjmc7): move into engine opts?

releasenotes/notes/agent-source-0d2b21262ed10d3e.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    A configuration file setting `[engine]/agent_source` was added.
+    The value is then used for the `pip install` command to install the
+    murano-agent. Since pip accepts http and git URLs, this can be used
+    to install agent from the custom git repo or install version other than the
+    latest.