tools/xenctx: Correct use of xc_domain_{, un}pause()

tools/xenctx: Correct use of xc_domain_{, un}pause()

The previous code never worked correctly.  There was a TOCTOU race between
checking dominfo and pausing the domain.

Since c/s 3eb1c708, Xen properly reference counts pause hypercalls, so
unconditionally pause and unpause the domain.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: George Dunlap <george.dunlap@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>