Your understanding is correct. The 6V Utility Channel (Channel 0) can only output 1A maximum on the PXI-4130 SMU.
If your load tries to draw more than the current limit (user programmable up to 1A on Channel 0), then the SMU output will go into "current compliance" which forces the SMU into constant current mode instead of constant voltage mode - as a result, your voltage will drop accordingly until V=IR. This behavior is often used to protect the device under test connected to the SMU. ...I might start by testing out the solenoid and seeing if it will actuate at only 1A, but the best solution would be to use an output capable of 2A like Channel 1 on the PXI-4130.
Also, please take note that heavily inductive loads can occasionally cause issues with the control loops on power supplies on SMUs:
http://zone.ni.com/reference/en-XX/help/370736F-01/ni_dc_power_supplies_help/4130_source_stability/
NI has recently developed some cool technology on newer SMUs that helps manage control loops under reactive loads:
http://www.ni.com/white-paper/13093/en/
For both points above, I might recommend to monitor what happens to the 4130 output as you actuate the solenoid the first time - either using the on-board voltage and current measurements of the 4130 (can read at up to 3kHz) or with an external scope on the voltage.
